The thing is just because the Overvoid was "drawn on" and was likened to a blank canvas doesn't meant that the supreme being is a literal writer.
The wole "Overvoid was drawn on without it knowing" was Grant Morrison making an anology. If the Overvoid is a piece of paper, then the multiverse was "drawn" on it. It discovers it, etc.
Grant Morrison in Animal Man and any other writer never made an appearance where they outright stated or even heavily implied that they drew on the Overvoid. That's where the assumptions comes in.
>Grant Morrison is an author avatar > Says he created Animal Man > is called the Writer > The Writer drew on the Overvoid
That's the assumption being made but there is little evidence to support it. This is no different than that offhanded appearance of the "Divine Presence" in I/O that was automatically assumed to be Tier 0 and everyone mocked it for such a loose-minded interpretation.
Even if this was true that the DC writers wrote on the Overvoid, it does not at all mean that The Writer is DC's supreme being. Grant Morrison said the Overvoid and the Source were God or at least forms of God. Not the Writer. If anything the Overvoid is the supreme being and it's only limitation is the result of fourth wall interaction. Not a single DC Comics writer ever confirmed the status of The Writer as a supreme being, they literally treat it as the staff at DC making the comics, and I read over the animal man comic multiple times, that just strikes me as typical fourth wall interactions with Grant's avatar literally saying no fictional character can ever reach the Real World and harm him. Sounds like meta-commentary. This isn't like Marvel with the TOAA where it once appeared as Jack Kirby in it's first appearance (during a Fantastic Four story) and was later consistently shown to be a fictional character, not an actual author avatar, confirming that the idea of TOAA being the writers at Marvel was, at least pre-retcon wise, a metaphor and analogy, not concrete fact.
So unless someone can provide definitive proof that The Writer is the supreme being with more than just those few little offhanded appearances of writer avatars that seem mostly unrelated, and the Morrison interview which I believe is unrelated to the Writer entirely, can we please just use our best proper judgment and determine the best solution for DC's supreme being? Be it the Overvoid, the Source, or the Presence, I don't care, it just doesn't seem to be The Writer. I used to firmly believe the Writer was canon but going back over the comics and interviews have made me reconsider, that's all.