Have an iPhone X and Apple watch series 5 paired. The iPhone provides the passcode to the watch. I recently had to restore my iPhone to a point prior to when I purchased my Apple watch. I was able to restore my iPhone, but I cannot reset/re-pair watch as the watch is still looking for the iPhone passcode to unlock.
Apple Watch Edition
While you can unlock your Apple Watch with your iPhone, you do not necessarily need an iPhone to unlock your Apple Watch. You can unlock your Apple Watch using its own passcode. This is the passcode you created when you first set up your Apple Watch. If you forget your Apple Watch passcode, you can follow the instructions here to reset your passcode: https://support.apple.com/en-us/HT204567
While you can unlock your Apple Watch with your iPhone, you do not necessarily need an iPhone to unlock your Apple Watch. You can unlock your Apple Watch using its own passcode. This is the passcode you created when you first set up your Apple Watch. If you forget your Apple Watch passcode, you can follow the instructions here to reset your passcode: https://support.apple.com/en-us/HT204567
iPhone providing Passcode to Apple Watch
