loveofdisney answered: I think part of the reasoning is practicality. Sizes make 2 piece costumes easier and hiding bra straps is easier with the shoulders covered
The separate pieces for sizing makes sense. I’ll buy that. But when it comes to bra straps and such… I think the bodice is thick enough that they don’t need to worry about bras, and if you look at the Tiana park costume, it’s a strapless dress and she doesn’t even have a flesh-toned cover over the shoulders. The same with Belle’s ball gown, which has a similar off-the-shoulder bit as Auroras. And Pocahontas’ one-shoulder dress.
I’m a nerd about this stuff so I’ve been looking up a bunch of the costumes just trying figure out the reasoning for why Aurora’s is the way it is. I know some things have to be changed for the ease and functionality of the cast member, but it just seems like they made it harder than it has to be on this one. :-/
Thanks for your input, though.