[Someone]

The post I replied to speculated that it would be possible to change the system's behavior without recompiling apps.

That would change the rules from "model updates and screen redraws never run concurrently" to "...will typically run concurrently". I think you agree that is asking for problems.

Of course, it is possible to adjust the system to apply different rules to different apps, but then apps would have to be changed to advertise "I am fine with running updates on a different thread". I think newer versions of Android already have some of that.