There would be absolute spoilers for Wool if others were read first. If you don't mind spoilers, that's fine. But publication order is almost always best. It's how the world came to love them after all. Why second guess the way the most people had no choice but to read them?
Besides... stories told strictly linearly are terribly overrated. I compare them to being spoonfed oatmeal.
I'm curious what your definition of a "true prequel" is? I don't really recognize different grades of prequels myself, and your definition of prequel seems to differ from mine.