who's Caro (Zhang or Kostner. Or is it a male skater I don't know?).
Caro is Carolina Kostner, who was given a level 4 at one of her 2007-8 GPs - NHK, I think. I'm not aware of any other lady receiving a level 4 at an international event. Zhang is usually referred to as Caroline.
I read somewhere else that a fan said that the rules are a bit vague in terms of how these are constructed, but I also know that two different performances of the same constructed step sequence could yield two different levels.
For reference sake, there were no level four footwork sequences at worlds 08 in the long program (8/9 quads, depending on how you count Weir's). It does seem weird, actually reading the facts, doesn't it?
What facts? That 8-9 skaters
tried quads? I can read protocols, you know

. I figured it was around that much, but the numbers have dropped in recent years, especially in SPs, which indicates to me that this element has been de-valued. And few skaters attempt two quads in an LP these days, even those who can do them fairly consistently. Now, some would say that's as it should be - but I disagree. As to quads and level 4 footwork, the difference, of course, is that it's very clear what a skater needs to do for a quad; it's not nearly as clear, as you noted as well, what a level 4 step sequence really calls for.
I would like to see the actual footwork emphasized and the rules clarified so that more of the top skaters can put the effort towards earning level 4s. Right now, the requirements are too vague, unlike spins and spirals where it's pretty clear - hold so many positions for so long, change edges at certain points, specific things that can be done as features, etc. Skaters who were considered weak to mediocre spinners have put in the work to make their spins better - because they knew what they had to do. It's ridiculous that so few skaters have been able to achieve level 4 step sequences, as compared to other called elements such as steps, spins, and lifts.
On top of that, I still think some of the requirements are not contributing to appealing footwork. Innovation is not being rewarded enough. Intricacy and flow are not being rewarded enough. Speed isn't being rewarded enough (I don't care if it counts towards calling the level or giving GOEs; it should count for more than it does now). And even if you play the game and do all that ugly upper body movement, high kick like there's no tomorrow and change directions so much the viewers' heads spin, it still might not be enough to get more than 3.3 base value and a half-point GOE.
Did any skater get a level 4 at 2008 Worlds, in either program? In any of the non-dance disciplines? I think nobody did. Not Jeffrey Buttle, who had lovely footwork. Not Dai, who has received level 4s before. Not Caro, who had done so earlier that season. And there were other skaters in Gotheburg who did excellent step sequences. Come to think of it, the few level 4s I've seen did not look more difficult or more innovative to me than many level 3s, whether by the same skaters who have gotten level 4, or by other skaters. So what made them so special? Was the technical caller in a good mood? Was it the 4CC happy hour? A going-away present for Plushy?
the latter I can write only because seniorita is on vacation and won't see my post.
I'm not one of the anti CoP people, but I really think that after the Olympics, the ISU will need to take a serious look at the scoring and make some significant changes.