Hammy is right. I think it is Tony Morris, the breeding expert in the Racing Post, who calls it "regression to the norm". The notion that no great racehorse can produce a better one than himself.
However Frankel broke all the rules as a racehorse, it would not surprise me one bit if he broke them as a stallion as well.
"this perfect mix of poetry and destruction, this glory of rhythm, power and majesty: the undisputed champion of the world!!!"