This culture of radical openness must be quite refreshing for people inside the company.

A lot of companies would never want this sort of thing to be out in the open. But really, why not? I imagine it helps to keep things sensible if you know that a thousand eyes could be trawling over your employee policies. You're certainly not going to be promoting astroturfing or other undesirable activities.

At the same time, you aren't burdened with deciding what to share. Many (most?) companies tie themselves in knots trying to decide what to share, and end up sharing nothing.

Sharing everything means less time spent deciding what to share and more time developing the stuff in the first place.