Custom transparency mode turns off on Airpods, when Apple Watch connects.

Whenever I put my Airpods on, the custom transparency mode turns off by itself, when my Apple Watch connects. I can 100% trace this to the watch, because if I turn off bluetooth on the watch, this doesn't happen.

Also if I go to the bluetooth screen on the watch, I can see that this happens right on the moment when the Airpods are shown as connected to the watch.