Also just tossing it out there, but SCOTUS saying "we need to do this to protect executive authority" when it's literally the executive branch arguing they shouldn't, sort of gives the lie to the idea this was about protecting constitutional departmental interests as opposed to protecting Mr Trump
The thing about the executive branch is they're super dooper jealous about protecting the executive branch's institutional interests. If a court ever finds itself arguing /against/ DOJ to "protect executive branch institutional interests" against *checks notes* DOJ, that's a bit of a tell