Umm, yes, it is, sort of. Default behaviour is that in low light condition kb light is turned on when slide is opened and then turned off with relatively short timeout (10 seconds). It is turned back on when any key is pressed. It is turned immediately off when
- slide is closed
- t&k is locked (lock button or systemui menu item)

I don't like original 10 seconds timeout (too short) and did not find way to configure it (unlike screen dim or off timeout). I often need to do some random first keypress (ctrl is harmless but shift or fn is easier to find in dark) before typing something. Also keyboard is too bright at night.

So yes, it is independent but I don't find it very practical. I would like to turn keyboard light off when display is turned off (for same reason, device is idle). With my current powerlaunch solution keyboard light is turned on indefinitely when keyboard stays opened.

I guess it is a matter of calling keyboard_light_off from correct place where display off event is handled, not sure where exactly it is.

As for sudo, yes, calling external code via sudo is a bit awkward for setting some value in /sys. Also it is not suitable for calling often (like on each keypress if I wanted to do keyboard light timeout + turning back on on keypress).