„Within range of one network“ doesn‘t give you as much information as „all these networks are visible and here‘s how strong they look from where you are“
I'm frankly surprised that the author of these tweets encountered this at all, much less was so annoyed by it as to troubleshoot.
That's not the trigger. The trigger is location services scanning for networks in the background. So, if you have that enabled then it happens automatically while you're on a call.