The Mandalorian comparison might also be alluding to how Mandalorian very obviously plays like a movie that got rewritten, split into parts, and had 3 bottle episodes shoved into the middle of it, and maybe they don’t want that to happen here, too.
But they could release it as a movie on Disney+ if they wanted, as well. It doesn’t have to be a “TV Show” - but I get why they’d rather have four weeks of subscription retention as opposed to one.