I don't understand the article. They either aren't clearly explaining the issue or just heavily misinformed.
I have Google One and PIA. Both do the same thing, which is add a key to the top right of the screen. To me, that's like a persistent notification.
PIA has never needed to use the actual persistent notification API. There's no reason to. Persistent notification is for application that don't want their UI Window to terminate when Android gets memory pressured, or when wanting to use a local service (eg: Location or Orientation) when not the main foreground application. I can kill the PIA Window (swipe up from recent apps) and the VPN is still running.
If Google One were able to activate VPN without changing my status bar, that's a different story, and that's not the case.
Edit: DNS66 as well