He's a man obsessed with beauty and perfection, but when he is slain he makes the most unflattering and undignified sounds that are not in character. Instead of leaving some witty parting words, he either breaks down and cackles wildly (evidently losing what sanity he had) or he makes these hideous gurgling noises of several variations or both.
Why?
Death is chaotic. Once Jhin dies there's no more beauty BS, there's no 4s for him. It's not pretty. He just died, there's no reason for it. He loses it therefor.
hard to talk when you get chopped down the middle by 
i would imagine
Well, he's sort of dying.
So I'm just spitballing here, but judging by the posts you make, it seems that gas has gone to your head.
Also have you ever met anyone who could control his death throes so it matches his character? His death sounds would be determined by what killed him most likely.
He's insane.
Really? I always saw Jhin's death (both in his animations and sounds) as a melodramatic spectacle, which seems very true to character.
When you die you die and you obviously would sound like you're dying.
Either he didn't die from a fourth hit and gets mad for not dying beautifully or he gets frustrated over not finishing his work. Also dying isn't pleasent especially when you get bursted by an assasin.
