I actually feel that the response here is a great one:

"I feel like you should be able (forced even!) to cite things that aren't journal articles- even blog posts- if they contributed to your body of work. But citing things that aren't prestigious reduces the perceived prestige of your own, which is a perverse incentive not to cite."

EDIT: I can't seem to figure out how to link to specific tweets, so this is the guy that said it: https://twitter.com/_delta_zero

He has a great point. If the proof is correct, you should cite the raw document. If you have to cite it through a proxy scholar, it feels like a form of gate keeping.