Something that some people never seem to consider is the concept of 'absurdly huge but still functional.' As much as I can agree that immobility is not the best thing to think about in real life, drawn characters can be depicted as being any unrealistic size and unrealistic level of agile. Sure, the absurd size and absurd mobility can be immersion breaking, but you know what else is immersion breaking? Choosing to ignore the follow-through just because it's gross in real life. Diabetics can still enjoy pictures of cake; SDC has no excuse for not drawing sizes that WOULD be immobile in real life but inexplicably aren't under fictional physics.
I think we can all agree that if we ever return back to Alex that we'd still want her to be double or even triple the size she last left on AND mobile. SDC can have her cake and eat it too, yet choosing not to because of real life squick is avoiding a problem that can be easily worked around for artists who actually try. Real life squick is not a reasonable excuse. She's a fat artist; fat people in real life are mostly gross. What she's doing with immobility as a concept is arbitrarily choosing to remind everyone of that grossness instead of making an effort to uphold the ideal fantasy. The fantasy that bigger is better and there are no gross sizes when the artist CHOOSES to cut the grossness out instead of giving it credence.
But NOOO, she'd rather say "It's gross in real life, so I'd have to draw it gross, and I don't want to do that" when that middle part can obviously be passed over.