Umbran said:
No, I think you are really missing the point here.
When you set an NPC's skill particularly high (or low), you don't need the numbers to determine where their skills and abilities sit - you've already decided that in your own head before you write down the number. If you already have decided what's going to happen, why do you need the number?
Because there might be as much as a 3-4 month gap between when I stat her and when she's used. Also because "Perform(Dance) +20" is just shorthand for "she's one of the best dancers in the known world".
The NPC creation guidelines are for creating characters - rounded, varied, multi-functional people. But in a one-trick pony like this, you don't have a character, really. The thing's only purpose in life is to set up or make high DC checks. That makes it more like a trap. Might as well treat it as one. Write down "Beat a DC 30 to win a dance contest" and leave it at that.
You're really just nitpicking the example and missing the idea behind it. Maybe if I gave a full example it would be better.
Stumbleena the famous Ballerina is afraid of her murderous former lover will seek to hire the PC's as bodyguards. She is an exceptional dancer, and has studied gymnastics as part of her training. She has lead a sheltered life thus far and is ignorant of the world, though she does have a sharp tongue from bossing around her servants.
CR -; Str 8, Dex 12, Con 12, Cha 12; BAB +0; HD 1d4; HP 3; Perform(Dance) +15, Tumble +8, Balance +8, Intimidate +5
... so maybe we wind up using her combat stats not because she is a challenge to the PC's, but because
saving her is a challenge. The Tumble score lets her dodge around a bit while her attacker is trying to grab her. Maybe she'll use Balance to do something dangerous like attempt to escape out on a narrow ledge. She's very fragile though so the PC's better act quickly. If the PC's investigate her background and want to know how much she's worth, I can quickly deduce from Perform to get her average income. So in my notes I would have only included the above line, and not this or the previous paragraph, because that's all I need to see at game time to remind me of these things.
Maybe I could have statted her using an NPC class, but my point is that it's just not always necessary to make it fit exactly. And if I did in this case, then all of a sudden she would have a BAB of something like +3, and around 15 extra HP's, and would be able to kick the crap out of a goblin warrior or two. All of a sudden she no longer fills her role in the adventure as well, and doesn't make as much sense in my setting.