Alright, so based on a recent failure on my auto-restart script it seems systemctl --quiet is-active <service-name> returned 0, which makes sense in a way with the obtained active(failed) detailed output I remember from an older failure case.

Solution is probably to check for is-failed instead, given that I don't have the need to auto-restart my service in case it was explicitly stopped (to what the original command shall return non-0 and its detailed output contain inactive, naturally), and given I want it to be restarted when failed.