Strictly speaking, there’s no formal rule - you won’t find a CBS/Paramount definition of “canon” anywhere that I’m aware of.

In practice, they stick with the tv shows and films.

But they’ve also worked very hard over the last few years to keep the tie-in novels and things like that “canon-ish,” in that they flesh out backstories from the shows, and the shows mostly don’t step on their efforts.

It sounds like the podcast is getting that treatment - as far as they’re concerned, this is what happened, and they have no plans to contradict it (and, considering the nature of the story, it’s not likely to come up one way or another).