I was in Frankfurt when OA was first proposed behind closed doors.
Those in the sciences who really need to know the results of a paper know about it way before the paper is even penned. I don’t know of any top scientist who waits for a paper to be published to get his/her data out there to be verified. The community is so small that e mail and a phone call really suffices in the transmittal of the information.
If a medical breakthrough is achieved, and that seldom happens, it is known ASAP. Accuracy in the published paper is more important than timeliness.