[Diemenz]

Originally Posted by Wormius

They should have had the update initiated by the device it is paired with. That way they could better control over compatibility issues. Or else checked the pairing on the watch itself and not started the update.

They do. WatchOS 6 could not be initiated by a device below iOS 13. However not everyone who owns a Apple Watch has an Apple phone so Apple allows you to update a watch to watchOS independently and puts warnings on the update page letting you know what devices (and iOS that is required) it is compatible with.