Pretty excited to find this. Got myself an old used Tektronix 2225 to try it out but turns out it didn't come with probes. Crazy stuff.
It's pretty fuckin' cool. If you run the Youtube video through an osc (I ran it through a DK MSD600M because I have one strapped across the mains) you'll notice that he's got some pretty brutal gating going on to keep the fuzz down but it's legit. I suspect his software captures square waves as "good enough" instead of showing the transients which allows him those nice, clean lines.