I have, for a while, noted that there is a difference between playing classical music and the old English/Irish dance tunes (or pieces written according to that style). I have characterized it as there is almost a sloppiness required in play the latter. A very calculated sloppiness, if that makes any sense at all. Rather than anchoring a finger on a note you will be back to before you finish the measure, for the most part, you lift that finger off the string.
But anyway...I finally came up with an anology for it yesterday while talking to Mama.
The difference between classical guitar and playing fiddle tunes on the guitar is like the difference between an English saddle and a Western saddle. (I've only been in an Enlish saddle once--and at that it was actually a Canadian Trooper saddle.)
It takes the same muscles and the same skills--just used slightly different.
I believe, to return to the guitar, that the so-called sloppiness is required because of the cadence of the music, whereas classical guitar music has an entirely different cadence. The muscles are the same and the skills are the same; just tweaked differently.
Just some interesting thoughts...(I hope.)