If I understand correctly, data like that found in Garland Tools (which I love) is obtained by data-mining the client. It is reasonable to believe that shortly after SE releases the new client for download, data-mining will begin.

Now, it seems SE has a policy of keeping some patch information back to prevent first-movers getting too much of an advantage; delaying the release of the new client until shortly before the servers go back live may be a component of that policy. In determining when to release the client, SE may be trying to balance typical download times against how quickly data-miners have been able to mine the client in the past, so that the data-miners are starting to get and present info about the same time that the servers go live.

Or maybe not. It's just an hypothesis.