I'm curious as to whether NSDR has any of the CNS benefits of sleep (wastes flushed during deep sleep, psychological healing during REM, clearing short term memory, spooling short term memory into long term).

Back when I was an undergrad, we had all sorts of gear for 'rat psychology', including deep brain stimulation. It was straightforward-ish to turn some of that into a 'Russian sleep machine' (low voltage surface electrostimulation). I used it a couple of times. The benefit was a full night's rest in a couple of hours - pretty handy to not need much sleep during finals. But even two nights in a row left me feeling 'odd'. I wasn't concerned for my health as I was an immortal nineteen-year-old, but that oddness kept me from using it much. Then I was on to another institution.

BTW, for anyone interested in taking that route, it's now called "trans cranial electrostimulation", doesn't take EE level ability to build, and they mostly run on the equivalent of a 9V battery. but I don't recommend it - I think I might have dodged a bullet, given how we had no idea about even just the glial system 's importance back in the 70s.

There's some new tcES stuff coming, mostly to help elders sleep. The notion is to monitor brain waves, and to 'sing in harmony' with, for instance, theta waves. Not cheap, but potentially helpful for people starting to have sleep issues - mostly as there's forward feedback loop (vicious circle) between the sleep center and Alzheimer's progression.