It's not unusual for cards that were printed, but never intended to be released to the public, to make their way out the back door.
Pro Set, for example, printed multiple cards of 1990 No. 1 draft pick Jeff George for the NFL draft so they could hand him a copy of his football card after he was drafted, but they had other versions that weren't supposed to be released and made their way into dealer hands, anyway.
In this case, these were the "1 of 1" Superfractors, so Fanatics wants to put a stop to it, lest there be multiple "1 of 1" cards of the same player.
I'm not a legal expert, so I don't know how strong of a case Fanatics has, but needless to say, their foray into the trading card market has come with plenty of legal cases (see the lawsuit between Fanatics and Panini) and issues with how some of their cards have been printed.