[SpaghettiCthulu]

Last I heard, the default on Android was to randomize MAC address across networks but keep them static for each network.

[homebrewer]

It's actually well documented. What you're describing is the default (mostly), but it's more complicated than that.

Proper randomization can be enabled through the developer settings.

https://source.android.com/docs/core/connect/wifi-mac-random...