This all makes sense to me (though I agree that Disney doesn't seem to use virtual carts for regular, Genie+ LLs). But what I want is an explanation for why the app constantly crashes and fails and/or an explanation for why Disney would use a virtual cart system in such an unstable IT environment.
I think we have all experienced the occasional IT failure on some other website -- you're trying to book plane tickets and the webpage freezes at the point where it is trying to process your credit card number, or something like that. But that rarely happens. And thus, the virtual cart doesn't cause chaos.
With Disney, though, the IT is as likely to fail as it is to succeed. Every time you go to book a ILL$ or a dining reservation, you have to hold your breath and hope that you don't get an error message, or get stuck in an endless login loop, or the like. I've seen Stitch eat so many pages that I'm surprised he hasn't exploded. Especially at 7:00 a.m., when the system is overwhelmed, things just don't work like they're supposed to. And thus, tons of inventory gets caught in the virtual cart, sewing chaos.