This is factually incorrect; last season I was in a 3 stack and received a message that said something like “server closed due to an unknown error” and got booted from the game. Upon reconnecting I was not suspended but I could not rejoin the game that was still running with my friends in. The game continued 4v5 and my friends unsurprisingly lost both the match and rank from this Blizzard error.
I’ve seen this bug happen multiple times now to multiple people and I would put money on this error counting towards the leaver total in a season. Someone who has had it happen twice and this similarly recent one where the queue bugged has just been hit with a season ban. That is nonsense and these penalties need to be rethought alongside the draconian behaviour related account actions.