What is the point of the comparison of Jesus' visit (parousia, Second Coming) discussed in Matthew 24 and Noah's flood?
The first thing to note is that the emphasis at Matthew 24:36-44 is that the flood came at them unawares, not that it was a worldwide event.
"For as were the days of Noah, so will be the coming of the Son of
Man. 38 For as in those days before the flood they were eating and
drinking, marrying and giving in marriage, until the day when Noah
entered the ark, 39 and they were unaware until the flood came and
swept them all away, so will be the coming of the Son of Man."
The emphasis can't be on the 'all away' part, because the very next line is
"Then two men will be in the field; one will be taken and one left. 41
Two women will be grinding at the mill; one will be taken and one
This new event will not sweep all away. Indeed the next line is
"Therefore, stay awake, for you do not know on what day your Lord is
The point of the comparison is vigilance and preparedness. Again, the quoted lines conclude with
"Therefore you also must be ready, for the Son of Man is coming at an
hour you do not expect."
Note that the implicit message here is the Son of Man will come at some point when some of his primary audience is still alive (otherwise, he could just tell them to prepare for the hour of their deaths). It will happen soon (similarly, Rev. 1:1's 'soon', Rev. 22's 4 'soons' and 1 'time is near', and indeed Matthew 24's 'this generation' or Matthew 16:28's 'some will still be alive'), before natural death for some of his primary audience. If this wasn't the case, what Jesus was saying would be misleading. Was Jesus intentionally misleading his primary audience? I don't think he was.
Having said that, using Noah's flood is suggestive of something over the entire Earth, if you believe Noah's flood covered the entire Earth.
So, what are full preterist views on Noah's flood?
There isn't any one specific view among full preterists on this, because the issue is somewhat orthogonal to issues within full preterism (just as, ex., Biblical Unitarians have differing views on all sorts of topics which don't impinge directly on the issue of whether Jesus is God, such as preterism or futurism!).
However, there is one interesting issue in particular. In the Olivet discourse, Jesus talks about 'the earth', and similarly, the flood covers 'the earth'.
"all the tribes of the earth will mourn." (Matthew 24:30)
Many futurists understand the word 'earth' here to mean what we mean by 'Earth', but the term in the Greek is more flexible and was used to mean a local area.
Similarly, in Genesis 6:13 (as one example among many in Genesis 6)
"Now behold, I will destroy both them and the earth."
Interestingly, no one who holds to a global flood believes God destroyed the entire Earth. So what was God saying here?
Just as the use of 'earth' in Matthew 24 is subject to a certain interpretation by full preterists, the awareness that it can mean a local area naturally applies to the flood account. For example, the article Noah's Flood: Global or Local examines this in depth, and mentions Luke's account as well. In Luke 17:26-30, the parousia is compared not just to the flood but also Lot, and Sodom's destruction.
"Just as it was in the days of Noah, so also will it be in the days of
the Son of Man: 27 People were eating and drinking, marrying and being
given in marriage, up to the day Noah entered the ark. Then the flood
came and destroyed them all. 28 It was the same in the days of Lot:
People were eating and drinking, buying and selling, planting and
building. 29 But on the day Lot left Sodom, fire and sulfur rained
down from heaven and destroyed them all. 30 It will be just like that
on the day the Son of Man is revealed."
As the article referenced above says,
"God destroyed ALL people in the DAY of Noah, in the DAY of Lot and
the DAY of Son of Man (during the destruction of Jerusalem in AD 70)
which means locally only, not worldwide."
Although I think the most straightforward exegesis of Noah's flood is a universal one (contra the author of the article), if you think the comparison in Matthew 24:37 refers not just to the suddenness but also the extent of the destruction, then the comparison to Lot in Luke suggests what is relevant in the destruction isn't that it is global but complete within a given area (ex., one city). So the 'all' in Matthew 24:30 here is contextual, and could refer to the entire globe (suggested by a straightforward reading of Noah's flood) or a local area, such as the siege and destruction of Jerusalem (suggested by the comparison to Lot) in AD 70.
The connotation in the comparison is not universality but utter devastation within the relevant context, and that is indeed what happened to Jerusalem and the Second Temple in AD 70.
Q. How do full preterists interpret verses 40-41: "Then two men will be in the field; one will be taken and one left. 41 Two women will be grinding at the mill; one will be taken and one left." Does it not sound like the ones who are taken are being saved from the impending destruction (just like Noah and his family were kept safe inside the ark)? This is commonly understood to be the rapture of the Church.
A. The typical take is probably that this refers to the many people killed and enslaved in Jerusalem. That's the view taken in the full preterist article Matthew 24 Commentary.
"In describing those killed by Noah’s flood, Jesus says that the flood
“took them all away.” [...] the flood in the analogy above represents
the Roman army. Therefore, those who were “taken” by this metaphorical
flood in v.40 may also represent those who were killed during the
Jewish War. The people who are taken away in v. 40 might also
represent those who were exiled during and after the Jewish War since
being taken away by flood waters representing the Romans also sounds a
lot like exile. Perhaps half of the people of Jerusalem were killed or
exiled [...] Matthew 24:40 is often mistakenly cited as evidence of
the rapture. Rapture theorists identify those who are taken in v. 40
as the righteous who are raptured. Preterist Author Charles Meek
points out that this verse does not appear to be referring to the
rapture since in the context of this verse those who are taken in v.
40 are the wicked, not the righteous, since it was the unrighteous who
were taken away by Noah’s flood in v. 39."