His original complaint being dismissed matters because it suggests that he was fishing around for a complaint that was valid, and that perhaps his primary motivation was to get money out of Google.

Legal nitpick - you can get away with alleging pretty much whatever you want in a legal complaint. You can't even be sued for defamation if it turns out later you were lying.

Jeff Dean isn't saying that Cheng et al. should be unpublished; he's saying that they didn't run the method the same way. It is perfectly fine for someone to try changing the method and report what they found. What's not fine is to claim that this means that Google was lying in their study.