The increased size is indeed very nice from an accessibility perspective, but it seems to me that practically everyone capable of going to the lavatory on their own is also capable of operating a (well-designed) mechanical lock on their own. And for everyone who needs help to do this it's a non-issue because the person helping them can close and lock the door.

The caveat here is that I'm not an expert on this, and that I'm possibly argueing from a position of ignorance. But none of the people claiming accessibility benefits (there are several) have made a very convincing case, beyond a mere assertion that it's more accessible. The door design as such is more accessible, but I don't think it actually matters in this context.