See, I read that as Google saying disavow is strictly for webbies who built significant amounts of unnatural links, which CAN be a Penguin issue but is not the only one.
Penguin definitely affected sites with clean backlink profiles, so it would not help those sites to use disavow. Might even make things worse. Penguin clearly deals with more "spam" issues than just backlinks. I mean, the old algo could deal with spammy backlinks and had been doing so for years - why build Penguin to do what's already being done?