Many AHs are built on the premise of a technological advancement ( gunpowder, printing, stirrups, etc) being developed earlier than historically.
But do we have any particular research on how quickly new technologies (we’ll define tech as broadly as suits the discussion, so everything from intangible ideas to new machines) spread? In particular, prior to the printing press, which kicks everything into a higher gear. I did some half hearted searching, but sadly, most of the hits were either about Crusader Kings 2 or modern technology - hardly applicable to prior eras.