Do people really need to be slapped on the face with a this is canon and this isn't to follow the series's (somewhat) mainstream continuity? Like:
We know that GT is a side story (Toriyama flat-out stated this).
A continuation to the Dragon Ball Z TV-Anime (As stated by Kozo Morishita, DB anime series's producer).
We also know Toriyama doesn't like the potrayal the anime team gave Goku as a character and that he had very little involvement on anything DB, DBZ and DBGT anime. He also claimed manga and anime are entirely different things in SGD.
So it is a stretch to say, "Hey, maybe this stuff doesn't really count in regards to the manga's continuity given what is mentioned above, the horrid contradictions created by TOEI's original writers trying to stay behind Toriyama and the original author's word?" I would say, no.
Also, how many series out there have a defined canon? because i haven't seen much of them and going by the original author's word and involvement is, afaik, something done with pretty much every series.