The Cambio Corsa's quirks aren't a result of it existing before more "modern" engineering was around; literally decades before the Cambio Corsa was invented, you could buy a production cable-actuated dual-pulley rear derailleur (i.e. the Chemineau of 1912).

Racing drivetrain design in the 30s and 40s was just weird. A lot of choices were made on assumptions that today look very silly, like that a tensioner pulley would considerably reduce drivetrain efficiency. Some touring and randonneuring and whatnot bikes from that era have ergonomics that could still be considered reasonable today.