This is more likely to happen on Amazon, than with a dealer that primarily sells and deals in cutlery. Bad news travels very fast in this community, if this were a common practice businesses could be shut down within days. Most companies though have authorized channels which they have used to secure their products, and it is guaranteed to be authentic. I don't doubt some scumbag is capable of doing what you suggest, but it would likely not happen on a large scale through dedicated vendors. Unless of course someone teleports into the factory late at night and swaps the real shipment for a clone version.
I'm not saying something like this would be common practice, lol. I am just saying one could fall through the cracks, and although buying through a rep dealer is obviously the BEST way to go, to say it is 100% foolproof - just is not true.