Sculpting no longer supports multires?

Im working on a sculpt only to find out the blender no longer supports sculpting on lower resolution multires.

Does anyone know when this bug was introduced? And when we may see a fix?

This is not a bug. It’s an intentional crutch made in 2.81, and will likely remain until the issue with multires sometimes destroying mesh data when sculpting on lower levels is resolved. Quite likely, that means until multires is reimplemented.