[deleted] dc32f0cfe84def651e0e ntop
Just testing quickly with my phone, the BSSID changed for mine when I turned off the mobile hotspot and turned it back on again. So, it appears to be random.
It looks like AOSP supports changing the BSSID for hotspots based on docs I read. I don't know if using a random BSSID each time is an AOSP default or GrapheneOS has changed some settings to make the hotspots act that way. As of right now, I'm leaning towards guessing it's an AOSP default.
A couple helpful docs I found:
https://source.android.com/docs/core/connect/wifi-softap
https://source.android.com/docs/core/connect/wifi-mac-randomization