First step for you is to go into knowndevices.xml and remove that line. While the signal will still be visible, it should no longer auto-pair. If you don’t know which line - delete all the individual <DEVICE> </DEVICE> lines, and pair to your trainer fresh as though this is a new installation of Zwift.
Context question: do you have an ANT dongle on your computer? ANT Controllable signals are recognized quicker than Bluetooth because the BLE Controllable signal won’t broadcast until Zwift has bonded to the BLE Power signal. I have this situation too, and I’m told it’s the nature of ANT vs BLE for the Controllable signal.