I see – that explains why the Shadows clipping mask corresponds to Lightroom’s Soft Proof gamut warning for Adobe RGB profile in my example. So it’s not a working space gamut warning but display gamut warning. It would be useful to have both (and also output profile gamut warning), like in Lr.
Another comment on the ICC profile selection in the Settings: the option to choose Adobe RGB as ICC profile for your display might be confusing people who don’t know much about colour management. The setting only works well if two conditions are met: 1) you calibrate/profile your wide gamut monitor to Adobe RGB space and 2) your wide gamut monitor has a gamut which completely covers Adobe RGB in all hues. My wide gamut Eizo covers 97% of Adobe RGB but its volume exceeds Adobe RGB at 107% (i.e. it goes beyond Adobe RGB in some hues but does not cover all the hues of Adobe RGB), so choosing Adobe RGB in the settings would be wrong for my monitor. The default option is the best and shouldn’t be changed, in my opinion.