Interesting experiment - I've read about treble bleed caps many a time, but never bothered to try it. I think my PRS has one, and it works fine, so I left it there.
You can definitely hear that it retains more treble, but personally I really like the slight softening of the tone when the volume's turned down on a standard pot.
I guess it's something that could be useful on particular guitars - like maybe on a Tele with a powerful bridge pickup, if you wanted a more vintage Tele tone with the volume rolled back.