I have used the SWITCH option in a widget that I modified from other versions and examples found in the forums.
I cleaned up my system after installing the Marketplace version of the binding yesterday, so no longer have any of my V1 THING and ITEMS to show this, but can restore a 3.4.2 backup to show this if you like?
HUE allows one to switch off the lights and turn them back on in the same state as they were when turned off - which we use a lot. In my case I hardly ever use the DIMMER, other than to temporarily adjust lights to suite a short term mood.
I am however OK with the SWITCH hidden in advanced - at least it is still available, so thanks for that.
I am not qualified to comment on how it worked in the background, or what the SWITCH was linked to.
Cheers
Mark
PS: These are some examples showing that the SWITCH was available (and used) in the V1 Binding: