With a J-frame and the tip of your thumb directly next to barrel cylinder Gap???
I think you would do that only once.
No. Geometry, at least for me, works out that my thumb is not near the blast. Even with my model 60 no problem. Haven't shot the Lemon Squeezer in a long while, but it's a one handed gun anyway.
Here's the bigger question. If you shoot revolvers with weak thumb on top of the grip, behind the hammer, how long before you grab a semi-auto and do the same thing?
A consistent grip insures that I don't get stung by either type of gun. Even my single shot (when I had one) was gripped with both thumbs parallel and forward (not one on top the other).