I was getting the impression that you are "selling" the fact that the performance of this knife is based on false advertising, and using personal anecodes and some anonymous people as a supporting argument. That's basically the only issue.

Aside from that, in my opinion dicing an onion is a much more simple task for a knife than taking a very thin slice of a tomato. And in both cases it is likely more about the technique/handling and the sharpening than the actual knife material or technology. But the average person does not care about those things, so this knife could at least in principle be something useful for them. Not for someone who is willing to invest some time in the aforementioned things though, like you (and me too, for that matter).