I think it must be more than an oversight. There must be a reason. I think it probably can not tell the difference between a Faraway Island Mew, and an event Mew from Gen III. Only the Faraway Island can be shiny. But I am too afraid to ask them, as like you say "they are mean." I assume part of their answer is going to involve that I know the Mew is hacked. I didn't do this capture to try to trade and pass off as legit, so I don't need anyone there jumping down my throat.
I wonder why you can't see the legality analysis. Did I need to do something other than copy the link?