Maybe they manually process large bets, but they are a sportsbook and probably have every right to do so.
As for holding a bet for 1-2 minutes, that has never happened with me. If it did for you, then I would agree and never place a live bet with them.
I don't think it has something to do with large bets because there's a few times where my live bet gets rejected by their system and I only bet small like up to 19.99 mbtc per match.