is a very valid one and one that you should consider as you are. If you want it and want to match the rest of the home, then do it, BUT my first concern is the type or composition of the sub flooring or the floor that the wood will sit on. If the sub flooring is any material made of particle or sawdust or wafers, remove this first. You could have a leak one time with a sub of particle even with real hardwood planks and the planks not be bothered, but the sub floor would heave up and mess the whole thing up.
I have installed alot of real hardwood in bathrooms. If all the prep work is done, from stainless fasteners to proper sub to sealing both sides of the hardwood planks, you will be OK. Maybe after an accident the real wood will expand a bit, but with drying out and time it will go back.
Go for it but do the under work properly and in prep for water eventually.