Just for the sake of this argument, I thought i'd add my opinion: Firstly I agree with Kawauso and Eldargal. Because Chapter House firstly were attempting to make Games Workshop kits... To me that seems a bit off and I'm not a fan of their style, but hey we all have our opinions.
However, when people claim that Games Workshop copies all of the aforementioned elements of fantasy and sci-fi it's because as artists and designers, everything you do has to be based in "real life" when you first start the process, because things need to look like they 'could' work, enough to keep up the suspence of disbelief (I think thats the term) and so when the Games Workshop 'copies' often it's a hommage, such as the "we'll be back rule".
But this idea of paying hommage to their predecessors I belive comes from Newtons claim that to get where he got, he stood on the back of giants (para phrased), also... Would anyone buy something with no recognisable links to anything ever previously made? (if even plausible). But yeah... I hope that made some form of sense .