This topic has been discussed often by Harald, Diana and other PMTS coaches. It is often hard to tell what is poor technique (under developed/insufficient PMTS movements) vs what is structural in one's body. All those that have had their alignment done by HSS know the large number of measurements that go into an alignment assessment and HSS is the first to remind everyone that what measures so in the shop is not always the correct answer once out on the hill. And refinements are made in camps and in private lessons once they can see one's skiing.
I am a great case study for the difference between measurements in the shop and the correct canting once out on the hill. I broke my right ankle many years ago and it was set wrong and it is set 12degrees or so turned out. This makes me quite knocked kneed on my right side. I measure for 4 degrees of shimming (out) to correct my alignment issue. And I skied at 3.5-4 degrees out (depending on which boot) for years. But several years ago I started skiing regularly with the appropriate level of CA in all my turns. When we get hip CA, we are externally rotating the hip (as much as it will go) and this prevents the stance foot knee from dropping inside (into that A frame position). Harald talks about great skiers from yesteryears on straight skis before anyone was doing any alignment work, and all the good ones that were knock kneed use extreme levels of CA to prevent the knee from dropping in. So quite interestingly I am now skiing with 1.75 degrees of canting (out) and I still measure for 4 degrees. This is a great example of how good movements are improving a structural alignment issue. And btw, If I had any more canting out, I would start to be over-canted and all the issues that come with that, with big difficulty in rolling over to the new edge.
At a visit years ago to a non HSS boot shop, they did some grinding work on my boots and then measured me in shop using a plum-bob. They got my right foot correct (at 4 degrees out) but they were also convinced that my left boot needed 4 degrees out which would have been horrific because I ski at .5 out on that side.
I think this a great case study and why on snow assessment matters especially as one improves with the PMTS movement patterns.