That second question is sharper: could the signal have looked different if the fix were wrong? In case one, the wake-log line was identical under correct and broken teardown, so it had no discriminating power for that bug.
The same applies to silence. Before treating no output as evidence, you need to show that the failure path would have produced an observable difference. Otherwise a healthy run that simply hasn't finished is indistinguishable from the failure you're trying to detect.
The frame here matches something we run into constantly on the config-change side: a query returning zero results is not proof of absence, it might just mean the query can't see the thing at all from wherever you're standing. What's helped beyond naming the claim a signal supports is asking a second question: would this signal have looked any different if the fix were wrong? The wake log line in case one would have printed identically whether the teardown order was correct or not, so it was never capable of falsifying the fix in the first place, not just insufficient. That's a slightly different test than "what claim does this support" - it's asking whether the signal has any discriminating power over the specific failure you're worried about, and it catches case four almost for free too: silence is only meaningful once you've confirmed silence is something the process is even capable of producing on the failure path, rather than something it produces on every path including a healthy one that just hasn't finished yet.