Why does WearOS require a phone to authenticate?

Watch: Samsung Galaxy Watch 5 LTE
TL:DR Is there a way to get the app installed without using a phone?

I’ve had the watch a year or so and I really only use it for time and for HA to track battery use. Occasionally for overriding lights, but that got less and less over time.

The watch recently got OneUI 6 installed and it lost connection to HA.
I was forced to reset the watch before I could set it back up.
With HA installed and set up again fine and it all worked happily.

I don’t connect it to my phone as I don’t use BT on the watch which wasn’t a problem before, but this time, after OneUI6 the watch was constantly nagging me to either “Connect to the phone” or “reset to connect another phone”.

I couldn’t find a way to stop it, so after a couple days I got p’d off enough to reset it and start it without the phone this time.

With no phone connected it won’t let you setup a google account for playstore installs, so instead I setup Wifi, enabled developer mode, ADB debugging and ADB installed HomeAssistant wear APK across to the watch.

Starting the install for HA it prompts for the HA address which I supply, but then it asks to connect to a phone to complete.

From memory it opens a browser to do the auth then hands it back to the app.
Is there another way of doing this rather than connecting to a phone?