What you’re saying isn’t correct, at least for properly configured private trackers and clients.
I did try that website and that’s the thing, the only torrents that show up are public ones. Torrents from private trackers like iptorrents are not showing on that list as expected. They don’t show, because they can’t access them, just read their about page and you’ll understand why:
Our system collects torrent files in two ways: parsing torrent sites and listening DHT network
Any private tracker worth your time has DHT/PEX disabled for their torrents because if they didn’t then the torrents were essentially public.