The MAC could remain unchanged for established connections while changing for new connection offers.
What does that accomplish?
It accomplishes what changing it in the first place is intended to accomplish - anonymity. Changing for established connections offers no benefits.
Hopefully just the process of watching all connections break and seeing the internet go away as the client reassociates with the AP each time they foolishly tumble their MAC on an _active_ connection will be enough to keep this scenario from ever playing out.