I think what's more likely is that they do the same thing that fantia does: if it's an image, they will insert some fingerprint data through steganography to trace which account leaks what image. Once their scrapers detect one, it flags the account that's connected to that identifier.
Subscribestar is trustworthy but it will just refuse to process if you have visited like kimono or some other subscription site scraper theres a specific type of cookie that it uses to do that which other websites like google and facebook use to track users even after a cookie wipe
