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.