jack destroyed the clock AFTER it was deemed just, even if it was a few frames; he had no influence on the outcome. it even chimed right before he hit it, indicating it was only the clock

That’s what I think as well, but the undeniable fact is that, Hussie intentionally left it ambiguous because he’s a Big Troll and wanted us to think about what makes a Death Just, because that’s just the kind of stuff we love him for.