Subtracting color or luminosity mask creates two masks

Please consider the following:

When I apply a mask, no matter which, and I subtract a selection using color range or luminosity range masks, in both cases Lr creates 2 (color or luminisity) masks.

Please see the screen reconding videos

https://drive.google.com/drive/folders/1ZxIIUnHnTNCRFzBuC92NuFS3IYJMUUQP?usp=sharing

Paul McFarlaine @3236367 Queen couln't reproduce the issue and suggested to report the problem.

Resetting Lightroom Preferences and setting the language to English (it was on 'Automatic'. My OS language is Italian) didn't solve the problem.

My workstation is a  Mac mini, OS Monterey 12.1, Lightroom (Cloud-based) 5.1.

Thank you for any help you can provide.