This is actually bad logic though. Alpaca is scum but he's right on this being an unreliable indicator!
If you think about it
situation 1. JK blocks scum -> the below choice is irrelevant. Scum will therefore kill assuming the later situation.
situation 2. JK blocks non-scum
choice A-> scum choose to no-kill, leaving the JK alive who may assume they blocked scum because of the no-kill
choice B-> scum choose to kill JK, but will possibly look bad in 3p if JK crumbed or made it obvious who he jailed (because it would make said person look good rather than framing him like a no kill would)
Or so it seems. But because we're in the (I think) lynch-one jail-one scenario, I believe choice A is instalose forcing them to attempt choice B.
But all this has assumptions. You can't assume mafia will play optimally, mafia may not assume town will play optimally either and so that may influence their choice too, etc etc. The game is unpredictable, I didn't think murph would do what he did because it was just scumclaiming fmpov, but it actually almost won scum the game! What I'm trying to say is that it's always more complicated and assuming no-kill = scum blocked and instavoting is dangerous. At any point in the game for example scum could have hit me (BP) and it would also have been a no-kill for example, and there's all the WIFOM too. It's harmless here and probably most times but operating on this might get you burned some % of the time.