Agree, maximum efficiency is an absolute - pretty difficult to obtain. But it is the idea I see the founders having strived for when the system was created
That's fine, people find different things useful. If you ask me about the efficiency of a round house, when throwing a roundhouse (punch or kick) you tend to leave yourself open as well as turning your center away from your opponent giving up equal use of both hands & facing to a degree. While it can be 'efficient' from a certain POV, there are most likely more efficient options that also work within WC's ideas of economy of motion. If someone chooses not to work under these guidlines, that's their choice - who am I to say what other people should do.
As a counter point, in a fight, most of the time the top of a person's head is somehwhat open. I've seen in silly point sparring tourneys where people jump up and tap the head top of the head for a 'point' - but I rarely would suggest targeting that in a real fight just because it's open. Efficient doens't alway mean the best option.
I never implied wing chun was a rule book you must follow forever and I agree with your definition of the basic principles of wing chun. And, I figured someone (most likely you) would nibble on that last bit about 'doing wing chun' which is why I mentioned 'let the flames begin'. To be honest, if someone's fighting strategy is to drop down into a turtle shell posture and then only attack by jumping in the air with spinning backfists, I would say they aren't 'doing wing chun', even if some think it's a silly term to say.