[johnm]

Can't speak for the GP but IME, absolutely. It's much easier to dig in deeper with (much) clearer signal about somebody when they are talking/working with their own code/project. Less distractions/confounding factors/proxies, more direct inquiry and you can go as deep and broad as you want to map the edges/gaps of not only what they know but what they care about/prioritize and why. The proof is in the code.