I still haven't heard the the rationale behind the opinion that Kaetlyn's case (at late age stable and success developing to the (7+2)-level) is not unique.
Kaetlyn's career may not be usual, but it is not entirely unique.
Shizuka Arakawa, who won the 2006 OGM, began skating as a senior like Kaetlyn, at 16. But during the first half of her career, she was attending school and skating was secondary; her results were mediocre. In 2002, at 20, she was skating full time and her results began to improve. She went from finishing 22nd at 1998 Worlds and 13th at the 1998 Olympics to 8th at Worlds in 2003, then a World Championship in 2004 and the OGM in 2006.