For sure, we can only evaluate what we can get access to. We're trying to scour as many sources as possible, but if you're exceedingly quiet, you wouldn't be in our system.
I suspect you're right, though I'd rather they share the non trade secret advice that they have in a more public fashion, such as a blog or stackoverflow.
I guess I'm gonna be a negative Nancy here, but I know some very good developers that don't make anything about themselves public. I expect some of the very best are completely invisible on the internet, at least by their real name, because they're too busy working on things their employers would rather keep as trade secrets.