This is why I'm asking whose definition it is. Whose idea was it to start using this term, which had a useful and important definition for generations, to refer to something else now, and then act as though everyone should just know this?
I'd assume it would have had to be somebody pretty important, for their fiat to have such weight. I'd like to know who it was.
I'm sure you can use on-line search tools to find where and when the term first appeared on the internet. My suspicion is that the phenomenon was being discussed informally between people who assess students' work, someone used the term "plagiarism", someone will have pointed out that it was "plagiarising" the student's own work, so the prefix was added, and stuck.
It's a concept that needs a name, and when a name turns up it often spreads quickly with no obvious source.
I'd assume it would have had to be somebody pretty important, for their fiat to have such weight. I'd like to know who it was.