That's canon, too. The canon hierarchy where TV shows override other forms of media no longer exists. Although contradictory, both versions of events should be equally valid.
Retcons are still a thing, though, which seems to be the case here.
In the novel, the 'battle' between Ahsoka and Maul obviously played out much differently than in TCW -- so the latter should become the new canon take on events.
Like you said, this isn't Legends where showings in different media just fall into different tiers of the canon hierarchy. So if contradictory events take place, then the most recent depiction logically has to be what we go by, because they can't both be canon(especially when said events are vastly different, like they are here.)