As cocktail historian David Wondrich alludes to in his introduction to the book, Jim Meehan's The PDT Cocktail Book is aiming to be the Savoy Cocktail Book of today. This is no small task: The Savoy Cocktail Book, written by exiled American Harry Craddock while tending bar in London during Prohibition, is a unique look at the state of the cocktail circa 1930 and arguably the most famous cocktail book in history. Apart from mimicking the title, Meehan similarly includes vibrant illustrations* and devotes the bulk of the book to a massive list of recipes. What's really amazing about this ambitious goal is that he largely succeeds: The PDT Cocktail Book is the definitive guide to the modern cocktail revival, and an essential addition to every home bartender's collection.
Sother Teague’s cited book does indeed have this as equal parts (1 oz each), while the more recent Imbibe page citing him moves the balance away from Chartreuse which I agree does seem sensible. If I had to guess, perhaps early on he borrowed the ratio from the Bijou (which the book cites as inspiration), and more recently decided to adjust the spec. I’ve curated the recipe to conform to what appears to be the latest version.
The version I found used repo tequila and different proportions (1.25 oz sweet vermouth and repo tequila, 0.5 oz chartreuse) which seems much more balanced to me. An oz of green chartreuse would be a big bully. https://imbibemagazine.com/recipe/bijou-riff-teatro/