I discovered this bug months ago with the previous version of iOS when my phone always seemed to want to connect to the WiFi OBD2 scan tool dongle I have connected to my cars on-board diagnostics port. The dongle communicates via WiFi (not Bluetooth) but doesnt serve as an internet connected hotspot.
Whenever Im in my car, the iPhone automatically connects to the WiFi OBD2 scan gizmo and prevents LTE wireless internet from working unless I tell my iPhone to forget the scan tool as a network. I suppose that the iWatch3 is unable to tell itself to forget the non-internet enabled WiFi network?
Was this designed by Goodwill Industries engineers? Sounds like a dumb ass screw up.
Yeah, it is too bad too. Because it would be nice to leave that dongle connected and monitor things.