I have contacted AppleCare Support today ... Basically there are two options:
1. Wait until next update which will solve the issue. And use code / no mask in meanwhile.
2. Workaround: - Make a NEW Back-up for the iPhone13 (Pro). - Erase phone and set up as new phone. - Restore from backup iPhone13 NOT from original backup (iPhone11/12 etc). - Go to 'settings' > 'Face ID & Passcode' V 'Unlock with Apple Watch' ... now the toggle switch and connection should work!
Please let me know if it works or not!
Edit: Worked fine after lengthly backup-restore process.. (Kept Data-plan settings e-SIM , but had to rebuild the rest .. such as ApplePay , 2 factor logins , and some secure apps)
Alkmaarder iPhone 13 Pro Max, iOS 15.0 (19A346) < This new iOS from update , NOT the iOS 15.0 out of the box!
Apple Watch 5, 44mm (no LTE), WatchOS 8.0 (19R346)
Apple Watch 6, 44mm (no LTE), WatchOS 8.0 (19R346)`