Pasting with middle-mouse button was a thing even before auto-scroll existed! And yes, for us who grew with it, its a damn good feature, I couldn't care less for auto-scroll, but I love my middle-mouse paste :)
Either way, it should be a configurable option, not hardcoded deep inside the bowels of the system, which appears to be the case as far as I have been able to determine.
For what it's worth Windows has (had? don't know about Windows 11) both of these, but they're either buried in the registry or need Microsoft PowerToys to enable.
I did manage to enable follow focus a while ago, but it didn't behave as I was used to (I don't remember the details), so I disabled it.