WRT the skill of "repairing the proprietary code," there isn't any repair of code (in the literal sense). It is actually the skill of clicking the right button

WRT the skill of "repairing the proprietary code," there isn't any repair of code (in the literal sense). It is actually the skill of clicking the right buttons (often in a horribly designed GUI) to make a proprietary machine do what it needs to do. Come to think about it, it isn't obscure skills, it is obscure knowledge. The problems are (a) there is really no skill involved, (b) the knowledge involved is specific to a proprietary machine and proprietary program, and (c) the training courses are training specific knowledge, not the principles and cross-training that would apply more universally. Mapping to our (geek) world, training obscure knowledge vs. actual skills is all the "office productivity training" that goes on which really is "which buttons to click in Excel"... leaving the trainee helpless in LibreOffice because the button is in a different spot and possibly labeled differently. Note that the trainer is not entirely at fault - I've been amazed at the number of trainees that cannot generalize.