Mine was stick to the lans like it was glued but in fact it was vacuum effect.
“It is a cushion rather than a waterproofing device.” Yes and not just that… It uses for proper centering lens from emitter.
But it still has o ring in a flashlight bezel, double oring at neck section, and thick oring at tailcap. You can toss and leave it in a bucket of water and nothing should happen.