The article doesn't even gesture at the reason why West Coast is disfavored by some: it's the white flavor. A lot of people feel that the White clique of West Coast jazz capitalized on the popularity of the genre without really contributing much to it. It was the safe, commercial style at the time.

Note that this isn't my personal take. I love Art Pepper. I can tolerate some Brubeck. But I admit there was plenty of slop in the record stores, too.