I'm well acquainted with the choreography of 'Theme and Variations', 'Symphony in C', and 'Giselle'. I've staged a 'Giselle' and could probably stage the other two, (with a little advance video studying).
In 'Giselle', as you have said Paul, it's the way the penche is done. I don't think a six o' clock penche is necessary. I love Makarova's develope a la second in her solo leading into the pas de deux in Act II. But there is something poetic about the high leg. It's not high for the sake of being high, or "scratching her head with her toes" as is asked in the first post of this thread. It's just in the right place, taste wise.
I do think they way the develope, or the penche is executed makes the difference. I've recently seen photos of a gorgeous NYCB ballerina (one of my favorites), in a past six o' clock penche in the 2nd movement of 'Symphony in C'. It just didn't look good.
Get out your video of Gelsey in 'Theme' and see her a la second, and her penche. That is what I like.
I don't think the leg to the ear (as it is more often done today), in a short or long tutu is appropriate.