Michelle Kwan, when the CoP came in, had to truncate her signature change of edge spiral. Why? She wasn't earning any extra points for those six seconds.
Not sure what you mean.
In the year Kwan competed under IJS, there was no feature for holding a single edge for 6 seconds. Ca. 2007-2010 there was -- if she'd been competing then, she would have gotten credit for holding the RFI edge that long before changing edge.
In order for the edge change to count, the whole time that it was a feature toward a higher level spiral sequence, the edge after the change of edge had to be held for at least 3 seconds. Kwan typically had not been holding the second edge of her signature spiral for long enough under 6.0, so she had to hold it out longer to get credit. Also, if the rules required a change of foot (always the case in the short program while Kwan was competing) and/or both backward and forward edges (required for higher levels), under IJS she also needed to hold those backward/left foot spirals for 3 seconds, which she had almost never done under 6.0.
Of course she wasn't alone in having one sustained edge in the spiral sequence -- gorgeous RFI in her case -- and briefer positions on the other edges. IJS wouldn't give credit for positions held less than 3 seconds, so everyone had to start holding those other positions longer, including Kwan. No one had to truncate anything except perhaps to save time. But if held with quality it would add to the GOE and be worth doing for that reason. And a year or two after Kwan stopped competing, holding 6 seconds was explicitly rewarded (and still is, in the unleveled choreo spiral sequence).
The one time Kwan competed under IJS she earned the highest score for the short program spiral sequence, so it was hardly designed to penalize her strengths there.