A welder can tell if you're any good at welding by handing you a blowtorch and a couple plates. A pugilist or swordfighter can see if you're any good by seeing you go through some forms.
It's the fundamental fact of all truth - science isn't knowledge until it's engineering Applies to fighting, applies to war, applies to political philosophy - that's the basics The advanced level is that the test of knowledge can't be subject to Goodhart's law