The bolded part is a pretty big claim. So liturgists who argues the contrary wouldn't be serious by your bias. 

My opinion is that both pre and post 55 have their good and bad parts. That's why many priests that use the 1962 books retained some pre-55 practices.
Contra factum, non argumentum:
Since every liturgist acknowledges the Pian rites didn’t exist before 1951, by definition they all acknowledge their novelty.