Joel Mokyr did a wonderful job in Gifts of Athena, but he has the strange Jewish predilection for conflating verbalisms with existence. He refers to “Knowledge of how” and “knowledge of what”. But these are verbal categories only. They aren’t causal categories.
I use the terms “Knowledge of Construction” and “Knowledge of Use” (how). While “Use” and “How” share similar properties, “Construction and What” are sufficiently different in properties to mean considerably different things.
“Construction” requires action in time. I have no idea what “What” should mean other than an empty verbal category. It’s a purely self-centered, experiential statement.
I am fairly sure that if someone says they understand something, it means a knowledge of construction. Whether they can use it or not is only a small portion of the possible domain.
(Properties: a)Construction, b)Use, c)Intended Consequence, d)Unintended Consequence.)