[not2b]

In many cases they (Google) don't know the impact of changes until they try deploying the changes, and there's ML in the picture, not just algorithms. As I understand it, they often run tests that expose the change to a limited subset of users first.

[xg15]

Yes, but they don't just do random stuff. They make changes with the intention to adjust the experience in certain ways, so making those intentions public is important.