The term raises questions: Okay, so, what does it mean? How 'pseudo' is psuedo? And that's the point: When you pseudonimize data, you must ask those questions and there is no black and white anymore.
My go-to example to explain this is very simple: Let's say we reduce birthdate info to just your birthyear, and geoloc info to just a wide area. And then I have an pseudonimized individual who is marked down as being 105 years old.
Usually there's only one such person.
I invite everybody who works in this field to start using the term 'pseudonimization'.
Even aggregated data will loose the anonymisation characteristics when we are speaking of low volumes of data.
Number of cancer patients in the area A: 1 Number of residents in the area A: 1