lol I re-read the entire message to find it but not the title…
Basically, you cannot have multiple phones paired to the same watch over BLE because that was never implemented in watch firmware. Those watches never used BLE on android previously, which is why it used to work (multiple BT classic pairings do work).
We disabled adding multiple pairings on the watch itself on the new watches (to prevent it being very annoying and randomly working sometimes), but on old watches like Time Steel, you might find that it works if you enable BT classic mode in settings.
FYI “it used to work but now it doesn’t” is entirely random - the firmware picks a paired phone and only tries to connect to that one, over BLE.