I agree that they should be essentially the same and if thumbs-forward doesn't work for shooting a revolver, it shouldn't be used at all.Switching back and forth from a semi-auto grip and a revolver grip I think would be a bad thing.
Unless, of course, someone knows for sure they will never shoot a revolver.
As an aside, I've known some people with a single defensive handgun, a revolver, who shoot with the wrap-around grip, where the off-hand thumb goes on top of the web of the dominant hand. I think that grip hurts accuracy and is clearly dangerous with autopistols. However, it does help control recoil. So if your accuracy standards are "minute of man" and if you know you're never going to shoot anything but a revolver, I don't care if you use that grip.
For me, I've been burned by gasses coming from the cylinder gap so it's automatic for me to let the last joint of my thumbs curl a bit when I pick up a revolver. I find that this means I don't maintain a strict thumbs-forward hold with autopistols. There's not much difference in the grips and there's often none at all.
I pity someone with huge hands, trained only on autopistols with a strictly thumbs-forward grip, who picks up a J-frame for the first time and fires a shot without due consideration of the location of the cylinder gap.