Facebook attempted such a thing already, and was caught exploiting it. VPN apps for the purpose of traffic control and monitoring are dangerous as they rely on

Facebook attempted such a thing already, and was caught exploiting it. VPN apps for the purpose of traffic control and monitoring are dangerous as they rely on some other party. I could do the same thing without ever needing a service for that. Setting up a monitored VPN gateway is no rocket science for me, I could do that, but the folks using crappy apps couldn't. And I would still need a way to map traffic to specific apps to identify unnecessary/malicious traffic. There is no other way as only via the internal iOS firewall. I wonder how the team behind that report managed to do that what they claim they did.