It is a cognitive world, so if cognition is responsible for Morgana's change in form, I suppose it could expand his vehicular form to accommodate for more Phantom Thieves. I'm not even sure how many are a part of Crow's team, but I do know that we're not typically one of the founding members in other worlds.

[Which is troubling, given his own guilt for being so lucky, though Crow is much worse in that regard. People like Magpie are the norm, as sad as it is, but that doesn't make them bad.]