Having "grown up" on free software, I've always been quick to jump into code when documentation was dubious or lacking: there is only one canonical source of truth, and you need to be good at reading it.

Though I'd note two kinds of documentation: docs how software is built (seldom needed if you have good source code), and how it is operated. When it comes to the former, I jump into code even sooner as documentation rarely answers my questions.

Still, I do believe that literate programming is the best of both worlds, and I frequently lament the dead practice of doing "doctests" with Python (though I guess Jupyter notebooks are in a similar vein).

Usually, the automated tests are the best documentation you can have!