We've spent time in very humid areas without hookups, so we don't use air conditioning. Our wood most definitely swells up, such that one door in particular has a problem closing. When we get back to air conditioning, or to a dry climate, it shrinks back after several weeks.
I've also noticed cracking along the glue lines on tables and cabinet doors. If a motorhome has spent a lot of time in Florida without a dehumidifier or air conditioning, then the wood probably has swelled up. If it has, then drying it out will probably shrink it.
That's why, when you install wood floors in a house, you bring the wood in and let it acclimate before installing it.
So it is a known phenomenon. What you can't predict is how much the wood in the motorhome will be affected. Probably not enough to be a deal breaker, but it does happen.