But once procedural knowledge is had, it also incorporates things like body memory and pure automatic habit, which, when observed in oneself, are just as likely to be rationalized after the fact as they are to be antecedently planned for sound reasons. It's also easy to forget the initial propositions about a mastered procedure.

I've also noticed this kind of thing in my martial arts training.

For instance, often times high level black belts will be incredibly successful at a particular technique but unable to explain the procedure they use (or at least, they'll be able to explain the basic procedure but not the specific detail that makes the difference). These details are often things the practitioner has learned unconsciously, and so are not propositional knowledge for them at all. Or they may be propositions taught long ago but forgotten (except in muscle memory).

The difference between a great practitioner and a great teacher is usually the ability to spot the difference that makes a difference.