The word "canon" has changed quite a bit over the years and has many meanings now, one of which is authentic work by the original author (or chose successor).
That is the definition we use must use when describing fictional stories.
Saying there is a "Real" definition is incorrect, definitions change.
Language is not static.
A scholarly website made by some random dude on the internet.
Thing is, I just realized, we're both using an argument of authority.
You are diving into the "Only X group of people get to define words" part, whereas I'm diving into the "Only the author is the source of a story"
I'm sure Blaziken is diving into something too