Oak floors don't absorb moisture from the top until the seal between sticks is broken, (Up to 9 or more coats of color and clear coat) cover the top. When it does its from the sides and bottom but pretty much negligible.
Flooded floors absorb from the sides and bottom and combined with absorption from the sub floor incipient buckling and heave rapidly occur.
Most of the swelling in all stick framed floors like Oak is from heat changes, and moisture rising through the sub floor from the humid basement. That's why houses that go cold during the winter have the most noticeable movement and gaps.
This effect is one of the main reasons why companies are moving toward prefab flooring using water/moisture proofing on the ply'd sub panel then gluing the finish surface to the panel.
There are very few drawbacks to the prefab method, one of which is the super thin protective surface coating,
2nd, (for me) the wider panels are much more difficult to profile to convoluted perimeters.
3rd, except for some of the higher end products there are limited opportunities for resurfacing prefabs, (the surface lams are too thin).
Lastly, even prefabs move around interlocking floaters require almost as much free space as stick builds and the gaps aren't recommended incase the house floods but natural movement due to heat changes.
Never bite the hand that looks dirty!
The more you know the more you're worth