I don't know what film you are using but most of the films I use, if I shoot 37th in 36exp film or 25th in 24exp film, the last frame is VERY close to end of the film where it is taped to the reel. I'm GUESSING what may be happening in your case is that winder tries to wind the last frame and there isn't enough left, so that it cinches the portion already taken up by take up reel to make up the difference - thus causing the overlap.
Personally, after shooting 24th or 36th, I just rewind it.
I wouldn't go by what Ken Rockwell says. Elsewhere in his web page, he actually says he does it for his entertainment and if you can't take a joke, you shouldn't be looking at his site. His claims are often very inflated. If he actually gets 38 or 39, good for him, but I really don't believe this is actually the case. Maybe in very small snap-shooter maybe? (where the distance between exposure opening and the canister is very small)