That’s the grouping screen (now called “Output Selector” for some stupid marketing reason).  For group volume control:

Group volume

Press and hold the volume slider on Now Playing to see all active products and their volume levels. You can adjust all products' volumes at once or adjust them individually.

https://www.sonos.com/en-us/guides/sonosapp#to-output-selector-passport

When I hold the volume slider the toggles on the other devices do not appear, see pic below