There’s a AnKing card that claims it’s specifically for active site covalent bonding but I don’t see anything online that explicitly limits it to the active site.

Feel like I’ve been catching a fair deal of errors like this on AnKing/MileDown.

It also had a card that said prosthetic groups have to be covalent bound but not all of them have to be covalently bound, just “tightly held”. And there’s plenty of real life examples of non covalent bonded ones.