I can see how he rejects 1945 as a dividing line, but technologically somebody could set a line between the kind of electronics involved in radio (circuits with say 10 vacuum tubes) and then television and computers. I like Brzezinski’s construct of the Technetronic age
https://www.e-ir.info/2011/07/22/review-between-two-ages-ame...
and feel the urge to periodize it into "lower", "middle" and "upper" technetronic even though we're way too close to it for that.