This question seems to hinge on the claim that it was a few years after the whirlwind had caught Elijah up that Elijah then wrote a letter to king Jehoram. This would indicate that Elijah had never gone to heaven, but had merely 'disappeared' for a few years, only to send a letter to Jehoram later on.
Interestingly, the account in 2 Kings 2 states that the group of prophets from Jericho (who had witnessed the event from a distance) asked Elisha to send them into the wilderness to search for Elijah. They reasoned, "Perhaps the Spirit of the Lord has left him on some mountain or in some valley." (2:16 N.L.T.) Elisha told them not to go looking, but they kept insisting. Off they went, 50 men searching in vain for three days. Wherever Elijah had been caught up to, he had not been deposited back on terra firma for that is the last mention of anybody ever seeing Elijah.
You then mention this letter Elijah wrote, "a few years later". But where, in the Bible does it say that? We can work out from the biblical chronology given what dates must have been involved.
Elijah operated from 874 to 853 B.C.
This period started two years before king Jehoshaphat of Judah reigned and included the start of king Jehoram's reign (which ended 841).
Elisha operated alongside Elijah for an unspecified time, before (literally) taking up his mantle. There would need to be exact dates given if the claim that Elijah continued living on Earth for a few years after the whirlwind event be taken as proof that he never went to heaven at that time. That exactitude is lacking.
The claim that Elijah lived on for a few years after the whirlwind event could be based on a theological stance that nobody went to heaven prior to Jesus' ascension, and assuming that "the heaven" involved could only mean God's presence. However, Young's Literal Translation has "heavens" in 2:1 & 11. Then the ball can be batted back by asking how come both the long-deceased Moses and Elijah appeared alongside the transfigured Jesus on the mountain. And the likely response to that would be "It was merely a vision - neither Moses nor Elijah were alive at that time." And so this will go round in circles.
The issue is not that Philip was taken up by the Spirit to be removed to another geographic location, to continue his apostleship on Earth. That actually has no bearing on what happened to Elijah with a chariot of fire and fiery horses separating him from Elisha so that the whirlwind would take just Elijah up and away. The issue is one of interpretation.
It may also have something to do with the similarities between Elijah and Moses' death on Mount Nebo. But the time of Elijah's writing that letter to king Jehoram only becomes a factor to consider if it can be proven from Bible chronology that the whirlwind event happened a few years before Jehovah got Elijah's letter.
As for my opening paragraph about the idea that Elijah never went to heaven but merely disappeared for a few years - that is demolished by what 2 Kings 2:12 says:
"And Elisha is seeing, and he is crying, 'My father, my father, the
chariot of Israel, and its horsemen.' And he hath not seen him
again; and he taketh hold of his garments, and rendeth them into two
pieces." Young's Literal Translation (bold emphasis mine)
If that supernatural event had not been a divine taking of Elijah away, once and for all, why would the two prophets and the school of prophets all have known in advance that that was the very day when Jehovah would take Elijah away? They were all expecting a miraculous event and they saw it. But why would God perform such a miracle if Elijah only had to be removed to another part of Judah for a few years and continue a very quiet ministry elsewhere, with an unreported death then? Why did what happened to Philip not happen to Elijah? Philip also had an encounter with a chariot and horses, but totally physical and natural ones! The Spirit saw to him getting back to where he'd been, supernaturally fast, but there was no flaming chariot with horses of fire, followed by a whirlwind catching anybody up to the heavens. Those are two distinct events. Their differences are clear and do not need to be 'explained', as if one contradicted the other. They do not.
