In my opinion, there is distinct discolouration there, that looks like it is from water, but not to bad. I did the transom of a boat years ago that was badly damaged and it was like scooping out custard.
Although not bad, probably a good idea to replace if you are going to do the floor and stingers.
I agree with Noel, unless you need to keep this boat for a reason,I’d be looking elsewhere.
It’s obviously your call.
Shakey - If only I lived near the coast