AngularJS code. I regularly dive in whenever I run into an obstacle.
The 30% figure is a wild guess, and may sound a bit large, but I certainly spend a lot of time reading other people's code. Or even rereading my own code.
Docs can be improved, absolutely, but there's no framework where I didn't feel that way about documentation. I don't think I've worked with any framework for more than an hour without looking at its code.
That being said, I'm not quite sure where that 30% figure comes from. Whose code am I reading? Why am I reading it?
Angular isn't your run-of-the-mill framework. They've reimagined almost everything. That's fine (and for the most part, I like what they've done) -- but documentation is incredibly important.