Earlier quoted context omitted.
IIRC (this is old and might have been wrong in the first place) iOS randomizes when it’s searching for networks but not when it’s connected to one.
It’s not a bad idea. A randomized IP address at each connection would break many things on quite a few networks (IP-MAC static assignments, for instance).
There are other options, like generating a Mac based off the real Mac and the ssid or bssid.