Hi Guys,
I think in any real out of air situation snatching the reg from the buddy's mouth is all you may have time for. I have practiced the without warning snatch, and I would say it is a bit alarming at first. It is the way I think I should train, and be trained.
In the practice scenario there is no out of air stress, the buddy is expecting and looking for the signal and is prepared to donate.
I expect in real life it may go more like this, breath out, pause, can't breath in, buddy finning out of reach and oblivious to your problem, when you get in range it will be to late to engage in polite hand signal conversation.