Yeah, I know, the scenario was intentionally unbelievable. The same applies to Dragon Ball-- it's licensed to Shueisha (to my knowledge, at least, Akira Toriyama has never claimed full ownership of the franchise), so pretty much everything they create can be considered canon in one form or the other, unless it's obviously set outside of continuity (like the One Piece crossover). As I said, if something they make directly contradicts something Toriyama established, then we can disregard it, but as long as it fits with everything the original writer wrote, it should be fine.
Fair enough, I suppose. I still really don't consider Bardock canon, since he was confirmed dead by Author Narration in the manga.
But, Alternate Timelines do exist in DBZ, so there's that.
Just as a reminder, the wikia is not exactly a reliable source.
For example: The wikia says about Bardock that he "is one of the few Saiyans to have gone to outer space and breathe normally, while fighting Frieza and his men.". But if you actually see the video clip of the fight, Bardock is not actually in "outer space", he is still inside the atmosphere.
The wikia also contains information about non-canon, mixed with the canon information.
Not sure if this was addressed to me, but I did use the wiki, so it probably is.
The wiki was the only source I could find that detailed the plot of Bardock's special and the subsequent adaptation. While all wiki's make mistakes, something as clear-cut as "King Vegeta was not in Bardock's special" seem like a reliable quote to go by.
I could, however, be wrong, as I haven't yet watched the special for myself.