I get why you all might suspect Xstar, any player that gets > 20% accuracy stands out from the crowd on the combogib server. In fact, I wondered about Xstar myself 6 or so years ago when I played with him on other combo servers. However, I don't think he is cheating.
With Xstar's ping at ~225ms and the demo perspective ping at close to 200ms we are looking at almost a 1/2 second delay in things the client sends to the server and the server propagates to the demo (especially important in the analysis here is view rotation). What we see between those updates is just prediction by the spectating client. This can make stuff seem jerky as you get those delayed updates.
Both shots happen after the enemy player crosses in front of the view of the player and I've even done my own natural snapping type shots in instances like that. If you look at Instance 2 at .25 speed, you can clearly see this wasn't a single snap-to shot.
Don't get me wrong, I'm not claiming this player isn't a cheater. I'm saying I don't believe he is cheating. He definitely has some experience in the game.
Almost 200 hours on London Combo in the last year:
And I think this is the same player who has 60ish hours on UK Insta going back to 2013:
And another 185 hours on the UK Combo server going back to 2013: