Spiral-projectors / holograms (?) - how do they work? (as seen in Gambinos SNL performance)

This thread on Reddit somewhat explains the effect:

A very clever use of the camera frame rate, rolling shutter, and a CMOS censor, combined with timed projection. You would only be able to see this in camera, not live.

Another user adds:

The laser fixtures are KVANT Spectrums.

And I’m not an expert on camera work but I do work electrics for SNL on their remote shoots and occasionally in the studio so! ( worked on the friendo therapy music video this week )

I was told it was a camera / shutter sync to the lasers which were programmed to make those effects but only on camera. In the studio it just looked like solid beams. They of course used some atmospherics to make the light a bit more visible.

Really cool effect they achieved they had a guy who specializes in laser design / effects and programming come in just to do it.

The person who claims to have produced this effect also paid a visit:

My name is Joe Picard. I'm a DP, I invented this technique several years ago and refined it with the help of Adam Labay. That was our work on Saturday. I like to call it laser-banding. We've done it for a couple other projects and have done some other special work together as well.

You can see some other cool things at joepicard.com.

In another Reddit thread there is a longer explanation, though this explanation gives :

Those Lasers were designed by the companies Future Weapons, and Nice Lasers, they are both champions of lasers (check out Gareth emery’s laserface video on youtube for more of their work!).

The appearance of moving lines is a process of lining up the frame rate of the laser lines being drawn with the framerate of the camera. the bent lines is an occurance of Rolling Shutter used in video capture.

In person, you can't see that effect, it's only visible on a recording.

Heres how it works: If you project a line that sweeps back and forth 32 times times per second, with a camera that only captures one frame every 1/30th of a second, you will see a pattern that oscillates back and forth once every 15 seconds (32/30 = 1 with a reminder of 1/16, giving the 16 second effect). Lasers of course use much faster drawing paterns than 26 "lines" per second, and this can allow a range of cuncurrent timings, if you notice there were several paterns being thrown by the ceiling mounted fixture, you can see that the fixture was capable of outputting several paterns at once, because it can draw 50,000 points per second, with a vector between the points

So what you see is 2D effect that make a 360 trip around Gambino.
Julius Popp created such waterfall to spell words. You can watch video here

Other videos usually are called "art of waterfall". This is to create this falling yet continuous area/surface.
Now you put that on a tondo and create extra moving part. In early cinema it was called Zoetropes (or wheel of life).

Think of a sheet of paper. Lay it down and make a small circle (or ship or pony) in left lower corner. Now drawn another circle little to the right and up until you end up in right upper corner. If you take this paper and roll it into cylinder from one point of view you will only see circle at some point. But if you spin it you will get the illusion of circles going up or falling (depending on which way you spin). Now just replace the paper with air and circles with short beams of light made by lasers and voila.