It depends .......... and I mean that with all sincerity. If the resort is pretty full, they need rooms emptied out so Mousekeeping can get them ready for the next guests.
Our experience (at WL several times, Dolphin, BC, Poly, CR, GF, POR) is that we have been granted a late check out of 1 PM about 60% of the time ----- it is absolutely, in no way guaranteed. Once or twice, it was only until 12 noon. We've always been told we'd be charged if we stayed beyond 1 PM, and that's exactly what others post. These trips were all in less-busy times (no summer, spring break, Easter, or holiday trips).
We've been told to call down on the morning of check out day.