I'm in Canada, I know the CSIA, I got a level 2 years ago, just to see what it was all about. I've skied with plenty of level 4 instructors, and while many of them are great skiers, I do think the CSIA technique is just a little lacking in the performance department.
CFSA (freestyle), and CSCF (racing), techniques are way more beneficial IMO.
You're right in that a good instructor will definitely be able to help this guy out in the moguls, but I think that given the choice of CSIA instructor vs Freestyle Coach, then a good coach would be a way better call, even for a beginner mogul skier.
CSIA teaches their own versions of "high performance techniques" on both groomed and moguls. Whereas, in my mind, if you're on a groomer the goal should be make a turn like a World Cup racer, not like a level 4 instructor.
Same goes for moguls. The CSIA bending forward at the waist style is just not as effective as the stacked, forward from the ankles position that freestyle ski coaches will teach. CSIA technique is more concerned with going around each mogul, whereas freestyle will teach how to go directly over the moguls, using a different body position that lends itself to much more effective absorption and extension.
CSIA is a great association, but honestly I think their technical stream is best suited for older people or non-athletic types who might not be fit enough to use alpine or freestyle techniques. I think anyone young and fit will get way more benefit from working with freestyle and alpine coaches.