You've left out the context of that quote to invert what the sentence actually said. Fayzullin's entire statement was:

    "[...] If you see that your .NES file DOES NOT match any
     of the ones found online, it is likely to be their own ROM dump.
     I have cut the ROM content out of the Wii file
     you sent me and it indeed matches the .NES file found online."

> it does not appear that they downloaded a Mario ROM

That is literally the opposite of what Fayzullin said.

The very next sentence in that paragraph goes on to say: " I have cut the ROM content out of the Wii file you sent me and it indeed matches the .NES file found online"

Here's some data that indicates that this "law" is generally not valid:

https://github.com/matslina/matslina.github.com/blob/master/...

https://news.ycombinator.com/item?id=9232419