As long as the user is playing, I don’t think this is trolling!
At any rate, a determined troll can do this by leaving browser tabs/windows open.
I imagine a lot of these players click automatch or create a game, forget they have done it, and just leave. I’ve done it once or twice in the past on accident (sorry!!!)
I’ve suggested it before, but I think the timeout on the first move should be much smaller (maybe 1 or 2 minutes). That way, the other player doesn’t have to think about when is a good time to cancel.