I think the P6 hair is intentionally low-res. The big problem with the P5 hair that came with P5 was that it was too high-res. Even if you had a really souped-up machine, collision detection didn't work.

But because of the way it's designed, it really doesn't dynamicize very well, desite the low poly count. In some styles, it goes through the character's faces, which screws up the dynamics. And even when it doesn't, the hair flattens unattractively when you dynamicize it.

I dunno...I suspect the P6 content was a last-minute rush job. Missing files, weird joint problems, hair that's tweaked for dynamics but doesn't look good dynamicized. You get the feeling someone ran out of time to test the stuff.