I can't say if that's true or not. But even if it is, they are hugely different in a number of ways. Spring rates alone as a lot different. KW doesn't make any other damper that links compression and rebound, Eibach R1's do, for instance.
Having spent some time looking at both, driving on both, etc. I don't see it. Normally it's pretty easy to tell when companies are hooked up. H&R dampers are made by Bilstein, and there obvious signs of it, as an example. I'm not saying that it couldn't happen, but if it is, it's a design built to Eibach's wants, not KW's simply relabeled. They are, look, and drive very differently.