The IJS separates the tangle of performance, choreography and interpretation into three categories in which the judges must simultaneously juggle seven bullets each. If that produces better results than juggling 21 bullets in a single category -- well, in that case I guess we are on the right track.
I think it does. For one thing, suppose each judge only manages to account for a total of, say, 9 bullet points out of those 21. Separating them into three scores will increase the likelihood of some of them representing each of the three different larger areas as opposed to one of those areas being left out completely.
Say you have only 7 bullet points:
a) harmonious composition of the program as a whole and its conformity with the music chosen;
b) variation of speed;
c) utilization of the ice surface;
d) easy movement and sureness in time to the music;
e) carriage and style;
f) originality;
g) expression of the character of the music;
Of those, I'd say that a, c, and f (and maybe a little bit of g) belong to Choreography, e belongs to Performance/Execution, d and g belong to Interpretation, and I'm not sure about b (listed under Skating Skills in IJS -- topic for the Speed thread instead?).
It's not very clear what all of those short phrases actually mean. I think what the additional bullet points in the IJS
Program Component bullet points do to a large degree is expand on the former Presentation bullet points. And then the detailed
Program Component Explanations expand on some of those bullet points still further. And some of the bullet points, especially those under Transitions, don't have official expansions/explanations. So in order to know what they really mean one would have to go through hands-on judge training and talk to enough judges to get a consensus of how they're using the bullet points rather than just studying a document.
But we're still two steps closer to sharing an understanding of what judges are looking at, or to judges sharing the same understanding, than when the only documentation was that list of 7 criteria with no written explanations.
(I'm leaving out the unison/shared responsibility/equal mastery bullets that apply only to pair and dance teams.)
When there were only 7 criteria listed, ideally every judge would understand all the implications of each of those 7 short phrases and apply them all to every performance to come up with one carefully thought out number.
But in practice they would most likely put most of their emphasis on 2 or 3 of those criteria -- whichever were their own favorites or pet peeves, or whichever a specific skater happened to be most obviously good or bad at.
If those 7 criteria are grouped into 3 separate components and judges have to give a mark for each of the components, they're a lot less likely to consistently ignore the same one. Instead, they may ignore the same subtle subpoint of one of those criteria, but at least they'll be addressing part of it instead of none.
And when the judges mostly agree that a skater was notably better at choreography than interpretation, or vice versa, for example, that gives the skater valuable information about where there's most room for improvement -- information that rarely gets past the judge's head onto written notes, much less all the way to the skater, when all the bullets are lumped into a single number.