In an old PRS video, which might have been from the late eighties, Paul showed that you could tell a wide/thin from a wide/fat by looking at the shape of the heel. I wonder if that's still the case.
If you look for "1990 PRS Video" on YouTube, at 20' 50" a very young Paul talks about the available neck shapes. I've just watched it again (it's been a few years), and he shows how you could tell the difference between a regular and a wide/thin back then by looking st the shape and size of the heel. He doesn't say anything about the heel on a wide/fat.
That's because WF was first introduced on the Dragon in 1992.
He does mention the wide/fat profile in the video, saying that "we put these on a lot of our Artist guitars". He just doesn't mention the heel.