It would make sense to disallow it just for parity with console players.

Souls speedrunners aren't really interested in parity with console players. Most (95%) don't run on console. For some games "Console" is a different category like with Elden Ring or there are only 3 runs on console in place 100+ like with DS1.

Also you can force close on console. For Playstation it's PS-Button + "Close Application".

For most categories it's disallowed (I think) because it's an out of game action, it's not using the game mechanics, but the operating system. That's at least the reason stated for Elden Ring speedruns. I couldn't quickly find a stated reason on the Souls speedrun wiki for the other games.