I can't really comment on how they do it. I can speculate, but there's already endless comments of speculation. What I can add is that it's to do with IP or DN

I can't really comment on how they do it. I can speculate, but there's already endless comments of speculation. What I can add is that it's to do with IP or DNS monitoring from the carrier or server. My SO who uses Verizon noticed it, and so I setup a home VPN for him, and when connected to it, all throttling disappears and everything is accessible at full 5G speeds. We have gigabit internet, so it's trivial for our network to handle the VPN traffic of streaming.