I actually saw people play out of sequence - some buskers or homeless or whatever people - just used to playing so many games against each other they'd get through the openings quickly by each person making several moves. It seemed too fast for me to see that they kept a correct pace, but maybe. I believe the games were very rapid. they stopped and started switching turns normally as soon as they were out of the opening. (so this refers to just a handful of moves at most.)
so with a bit of sportsmanship it's possible to actually play that way over the board with somebody who's cooperating with you to get through the opening quickly.