Unlocking with Apple Watch is not available while you screen is being shared

I've been getting this error since upgrading my MacBook to Mojave. Though "Unlock with Apple Watch" hasn't worked in a long time, as far back as Sierra.

I've gone so far as to reinstall High Sierra and import from time machine... reset and reloaded my Apple Watch... and reset/reload my phone/replaced a phone... to no avail. I even took my MacBook and watch to an Apple store to solve the problem, but they had no solution for me.

When I first noticed this message Screen Sharing was enabled... but I have since disabled it. Remote Management was never enabled on this mac.