The Son has the ABILITY to know but he does not have the AUTHORITY to know.
A Classic example of this is found in John 17:2 where the Father gave the Son AUTHORITY to give eternal life which means he has the ABILITY to do so.
After his resurrection, he was given ALL AUTHORITY to use his divine nature and therefore, he knows both the day and the hour of his own return ( Matthew 28:19).
Jesus has power and this power cannot cease to exists.What he doesn't have is the permission or the right to use it because he is the Son.
The truth of Mark 13:32 are these two:
1) Functional Subordination- the Son is not equal to the Father in role, authority and function.
2) Ontological Equality- the Son is equal to the Father in nature.
Ability- the quality/state of being able to do something.
Authority-the freedom granted by one in authority i.e. right
Nature- a set of traits/attributes in a person/thing.