Obviously an outsider should stay out of it, but equally obviously Player A was a dick.
So many ways of addressing this....
If Player A only wanted to win $80, then BEFORE THE MATCH BEGAN he should've either told Player B that up front, or---now here's an original idea that nobody in the history of pool has ever thought of before----suggest an $80 FREEZEOUT, or a 4 sets ahead freezeout if they want to play for $20 a set.
Or just say you want to set a time limit, which is fine, but say it in advance, not when you're already 3 sets ahead. That's just creepy.
But if you want to be a dick and quit while you're ahead just because there's no law against it, at the very least you should come up with an excuse that's a bit more creative.
Like the late Michael Gerace (AKA Geese) once did, when he got 8 games ahead of a hustler from New Jersey, let him win back one game, and then said
"I've got a doctor's appointment" and packed up his cue.
Funny, but none of of in that Randolph Hills pool room had ever heard of many "doctor's appointments" at 8:00 on a Saturday night.
But then Geese was a true original.
And then there was the one and only Murphy, a sidekick of the late H Street Fats, a local DC scuffler. His excuse for quitting after some poor fish had finally won a game after
14 straight losses was one that deserves a place in the Pool Hall of Fame:
"TOO MUCH SEE-SAW".
Murphy was so famous for this exit move that every time I've told this story to someone who knew him, the person I was telling it to would always just laugh and beat me to the punch line.