Not unusual in areas with high water tables...and gives the termites
something beefy - the posts - on which to chew.
These houses usually use 2.5 CCA posts and there isn't much that can
eat them. I still have some cutoffs from a house built in 1980 on Pine
Island and I use one for a bunk for my jon boat on my dock. It still
looks brand new. I have couple more that I keep next to the garage (in
the grass) for blocking up my trailer when I am working on the boat.
Same thing, still look new.
There were a few in Jax where the posts either were rotted out or were
eaten. I have no idea how the posts were treated. Most of the raised
floor houses I saw there, though, were on short concrete piers.