I like John Mueller and how easy it is to reach him on Twitter. He was definitely a good choice for a Search Advocate to be installed after Matt Cutts left. But, I would take everything he says with a big grain of salt.

It's in his best interest to say things like, "Yeah, we don't use page authority for ranking signals", when clearly they do. Just don't tweet this stuff to him directly or a brigade of "seo experts" will flock on you like crows on a shiny piece of metal.