Obviously a confused seller. Neo·Geo Freak was put out by, uhhh, well I forgot the exact co. name & don't want to put an "I think," however the publishing company was owned by SNK, so effectively the game would have to be SNK-authentic. That blurb about the box makes it seem as though it was something out of the ordinary to begin with so.....
It's no mystery. He's selling a Shock Troopers cart converted by NGF (US). He obviously got it second hand from somebody and assumes, like most people would, that Neo Geo Freak means the Japanese mag instead of the US rip off company.