Google because we feel there are enough webmasters and SEOs who are seeing evidence of such a change. To not report the change because Google has not given us confirmation would almost be unfair to the hundreds of webmasters asking why their rankings dropped or increased suddenly over the past week or so.
To summarize, we see two different update cycles from Google in the past week or so:
(1) October 14th through October 15th, that I personally believe is an ongoing Panda rollout.
(2) October 20th through October 21st, that I personally am unsure if it is Panda related or something else. I suspect it is a mix of Panda and potentially some other ranking adjustment Google may have made.
If we get a statement from Google, we will update you immediately.