Which is I why I used words like "usually" and "less likely." It's not any sort of guarantee of safety. For example, xFinity/Comcast owns NBCUniversal, and as such is technically the rights-holder for NBC content and as such they have a vested interest in potentially inspecting your traffic directly for torrents they have ownership of. In other words, I agree with your assessment here.

Private trackers usually have a limit of active torrents you can have depending on your ratio tier. Sitting on every torrent in a private tracker for one user would be a huge red flag, so the only way to have it work would be to have many accounts. Even then, unless they're seeding content, they will probably be kicked if their upload is 0 bytes after a month or whatever interval accounts are purged.

Sure, there are probably some studios going after high profile torrents on private trackers, but thinking they would be monitoring thousands of torrents is a stretch.