This article is disputed by others, so consider it one person's researched opinion and take it as you wish I think: http://www.seriouseats.com/2016/07/fake-kobe-wagyu-beef-japanese-steak.html
The general statements are that almost all claims of anything severed as Kobe or even Wagu are likely false or misleading. Now, the author makes his money by writing about fake foods, so has a vested interest in such claims, so that should influence merits, and saying something is a Wagu slider that was made with part or all US Wagu, is that fake food, misleading, or honest? Your call on that.
But, personally, I think you probably made the correct call. I would expect something called a Wagu slider would be one that might have some amount out Wagu trimmings added, but not enough to really be the correct us of the meat or representative of the name. The same went on for some time with Bison meat, a wonderful alternative to beef if properly prepared. But for years, it was difficult to find anything but tourist stop samples as over-cooked burgers and meatloaf that was likely about 10% bison and gave people a very poor introduction to a fine meat. That also is opinion, not backed by evidence other than person anecdotal experience though, so no one yell slander please.