It feels like a game of telephone from "he knew his gun wouldn't cycle so he was prepared to do it manually" to "his gun was like that on purpose so its extra quiet" and finally "he is using a super special cool gun(that presumably would be so distinctive as to be easier to track.)

Just from the motion in the video it blatantly does not look like a bolt action being operated, so I can't imagine it's the vp9 people are gushing about.