I'm not entirely sure, but since phones can auto-connect to wifi access points, there'd have to be some scanning going on if wifi is on. AOSP does MAC randomization for access point scanning too. Not sure if GrapheneOS uses a unique MAC for each scan + each access point or not, but I'm guessing they do.
katemason I have WiFi scanning disabled all together
Is this the option in the location settings? If I understand correctly, that one allows for scanning for nearby networks to assist with location even if wifi is off.
I guess the only way to completely turn off scanning is by turning the location wifi scanning off as well as wifi. There is a "turn off wifi automatically" setting, which could make this easier. That's at Settings > Network and internet > Internet > Network preferences > turn off wifi automatically.
Maybe the phone will stop scanning for known networks if you turn off connect automatically for all saved wifi networks at Settings > Network and internet > Internet > saved networks > network name > auto-connect.