Also, depending on the system, time spent on hardening is many times happening concurrently with some other tasks.

Maybe you trigger a load test, or run a soaking test or whatever, while that runs you do something else, pause and check results, metrics, logs, whatever.

If something is funky, you may fix something and try again, get back to your other task and so on.

It's messy, and keeping track of that would add significant cognitive load for little gain.