This is why I'm glad it's day 1 gamepass - if it sucks or is unplayable then I didn't waste any money.
But so far I've played every Bethesda game(elder+fallout) since Morrowind at launch - apart from their MMOs - and while they are buggy, none have been unplayable or unenjoyable due to their launch bugs. So hopefully this remains the case.
I mean jokes aside, usually preordering digital titles lets you preload most of the content several days before the release. If you don't have high speed internet, or have a restrictive daily cap - this can give you a leg up on a purchase you were going to day1 buy anyway.
Then on release it just activates your license and then you can spend most of release day playing the game versus waiting for it to download.