@bold, A simultaneous release is just that difficult. Porting from PS4 or PS5 to Switch or vice versa requires basically making a new game. Capcom thought it was more worth it to do just that, and made Rise.
Porting up to a more powerful platform is pretty easy but the downside is it would look outdated by the powerful system's standards. It wouldn't be as noticeable as Portable 3rd HD ver though lol.
DQXI was "reworked" on Switch (it took a while as it required remaking things) as DQXIS, which was then ported up to PS4 and PC for the added content. As a consequence, XIS on PS4/PC was a clear downgrade from the standard XI. They opted to port up the existing Switch version rather than adding the content into the standard game coz it's easier and cheaper.
Monster Hunter Rise on PC is probably taking a similar path where it will technically be a downgrade from World, even though the engine powering it is superior.