Nope you are wrong.What do you think that the XsX version is?
Besides, what do you think that these launch games are on both systems??
They are just cross platform games with performance patches.
BC games on xbox can be patched in whatever way the developer wants, it's basically the same as upgrading a PC and increasing the settings as high as the hardware can handle; on PS5 they are limited to unlocking the framerate (up to 60fps only) and/or pushing the resolution to the upper limit of the original PS4/Pro game.
Launch games, like Assassins Creed Valhalla, are native PS5 games and have full access to the hardware power and devs can do whatever they want with resolution and framerate and other settings.