Another MSQ roulette post: We need change on some level

[Kirika-]

No it isn't. There are buttons to leave group. You can leave for any reason you want.

It is.
And, yes, it is enforced and those found in violation are punished.
Section: Obstruction of play - Intentional leaving or disconnection

As to if the player's who dropped have a "legit" reason other than "I didn't want the lesser exp run, so I dropped", that is up to the GM's to investigate.