Why wouldn't they do this? It's good marketing, you can tally it up as a recruiting expense, same way/reason companies sponsor conferences and send people to speak. These days I see the term "developer evangelist" bandied around a lot -- it seems like they basically get paid to hang out in the dev community, make cool things with the product (tm), and then talk about it at conferences. These days I also see more and more ~1 hour informercials for product X at conference Y.

One, two or ten projects cannot possibly reflect people and decision making processes of an entire culture -- The best it can tell you is about that team inside the organization. You could only tell the culture of the company in aggregate, and companies where the F/OSS output is anywhere near the total of what they produce is pretty low.