The 130mm short Campag post existed because in the late 50s and through the 60s riders used big frames and did not have a lot of seatpost up. Saw a lot of them on complete bikes, never saw even one in store inventory. The 27.4 post was for light 0.8/0.5 seat tubes. Also happened when joker mechanics with expansible reamers confronted a big name frame with the seat tube brazed in upside down. Instead of sweating over all the metal that had to be removed they would laugh and make the frame into a 'secrets of the pros' bike with the big post for the supposed ultralight frame.

The 26.2 post for Cinelli is a hallmark of the old ones. There is a liner brazed in the tube. Cino had had frames that cracked there and he made sure it would not happen on his own bikes.