"The task he recommended as a quick break just happens to be one of the hardest games around, and a game that is despite appearances, all about going really really fast."

It didn't "just happen to be" anything. The whole point is an exercise that frees up your brain up from whatever else it was doing. The whole point is that it's hard and you are forced to think about it. Your mind can't wander back to what you were working on in bughouse, much less without a partner, because the game demands your attention.

"All good players play 2min bughouse, go on FICS and type "best B" and look through the game history. Or just look at the games in progress, it's all 2min."

This might be relevant if we were talking about good/high level players. We aren't, they are new players and they are playing OTB and most new players playing OTB play 5 minute bughouse. Yes, true statement, full stop.

"Similarly you claim that taking 2-5s per move is superior for new players. This is 100% false. You will get a worse record if you do that."

I would but a new player wouldn't. What's semi-optimal in bughouse is to make a strong move as fast as possible. A strong player can choose a reliably decent move in less then a second. A new player forced to move in 0.5 seconds as you suggest will make terrible moves and probably lose on both boards.