I don't think you can conclusively really dictate any of this as cheating. Forgive me being less knowledgeable about server mechanics at this present moment in time but from what I can see from this theres not much to go off of. On one hand, it could be silent aim. Bearing in mind theres no visible FOV circle though in his POV, something of note.
Unless something was detected (Aimbot pretty much always is if a good anticheat is running), Its very iffy.
He could well be cheating for all I know but if this is really the only clip that "proves" It, I would argue its not much to go off of. It could be anything, spread, server fuckery, All sorts.