was private address enabled in the 2.4 in the phone settings before? (not the watch app on the phone, the settings for the phone itself)
wondering if the setting was "syncing" from the phone to the watch.
the watch will naturally use the lowest power radio available, and power off the others, so as long as your phone is close then the watch will only have the bluetooth radio powered on, if it doesn't see bluetooth for a bit, then it turns on wifi. Same applies to cellular, it will only power that on if it can't find bluetooth or wifi.
so depending on the size of your house, and how far you're able to get from your phone when you set it down. The watch might not switch to wifi that often.
Yes the Phone was set to use private address for the 2.4 Ghz network but it was also never using that network. It was in the list of My Networks but not set to auto-connect and so never used. Either way the setting on the watch should surely be independent of all of this? It has its own MAC and IP address. It's a separate networking device. Otherwise the setting should not exist in the watch settings on the watch.
PS. I'm aware that the watch won't always use Wi-Fi but the annoyance was that it would keep overwriting my toggle when it did, thus re-enabling private address and choosing a new MAC. When all's said and done, the watch was literally overriding the manual toggle so it's definitely a bug.