This is what the journalist/food researcher, A Marzo Magno, thought was interesting as her giving the example of Cynar provides a time frame for when she collected information about Spritz, and that was at some point between 1952 (and even faintly possibly 2 or 3 years earlier than that as Cynar was being trialled in a couple of bars in Venice and Padova before it was fully launched commercially) and that point in the 1970s when the book was ready to be published.

I’m having trouble believing that it took ordinary Venetians over 20 years to work out that they could drink Cynar in this peculiarly Veneto style.

—-ETA:
The Società Dante Alighieri accepted and includes Mr Marzo Magno’s research on the Spritz’s origins as part of its History of Italian Food series.
https://en.wikipedia.org/wiki/Dante_Alighieri_Society