My Opinion: NewPipe, Piped, Invidious, etc's days are numbered.
With Reddit shutting down its API setting a precedent in the corporate tech world (and Reddit was a major outlier in that a ton of their users are technical minded and support third party clients, YouTube does not have that kind of userbase and will not get backlash for it), Twitter doing whatever the fuck they're doing, and Google already hellbent on destroying ad blockers, the days of Newpipe, Invidious, and Freetube are numbered. Wouldn't be surprised if they implement Netflix level DRM tomorrow that makes alt clients impossible. I say savour your alt clients while you can guys, you won't be able to soon.
I think they mean something like widevine a la Netflix. Granted there are bypasses for some levels, but that could be a problem imo, iiuc that's why there aren't any alternate frontends for Netflix or HBO. I think that would also potentially mean issues playing YouTube in chromium or firefox on Linux if they used L1 (not sure what the current state of widevine on Linux is, last time I had Netflix I couldn't watch on Linux and had to use my phone or Chromecast)