Beta is one thing.
The machines have less RAM. You can easily starve the GPU on these old models when Stage Manager is active.
That’s what Apple highlighted in their note.
I did so after multi tasking a bunch of stuff and stress testing. Took me 2 hours to find out how to slow it down.
Good example, watch some movie streaming apps and try making long posts or long documents at the same time.
Well as others like Mac Rumors staff said it’s working fine, let’s wait till the final release before claiming it doesn’t work as well with multiple things on the go at once? I can’t personally test it as I have an M1 iPad Pro.