New HotKey: "Watch Face" (Hold BACK)

I notice on my Fenix 7 that there's a new HotKey function called  "Watch Face", set by default under the "Hold BACK" key, and that when my watchApp is running, that function displays the watch face with my app still running "in the background", but, obviously, not displaying the app's view nor responding to user input.

On an F5, this "Watch Face '' option is not offered as a function for a HotKey. 

This Watch Face feature provides the opportunity for the user to activate the access glances  with the UP/DOWN keys with the app still running.

But interestingly, that HotKey doesn't "fire" from some of my views, which leads me to suspect that there's something in the View's Input Delegate that can influence the HotKey's operation.

Is there any documentation about this? I have read the Glances section in "Connect IQ Basics", but it doesn't cover the interaction with a CIQ app.

I guess it's a CIQ 3.1.8 (F5)  vs 4.0.6 (F7) thing.