I don't really see why this is an argument, if I'm being honest. Grant Morrison seeing no real line between the DC multiverse and the real world is not only well established and consistent across a staggeringly large amount of his stories and interviews, but it's also very clearly present in all of these
specific interviews and comics and the Animal Man run this cosmology is directly linked to. That run introduced the idea that the blank canvis was the bottom layer background for all of DC's reality, that Limbo was where all retconned characters and creatures went when no longer in continuity, and that it was all placed here by The Writer, who appears as a literal representation of the real world Morrison. Grant Morrison even cited Brain Bolland's cover for
Animal Man #5 as direct inspiration for the ideas he was exploring in Final Crisis.
I also think it's pretty obvious the scene in Superman Beyond is referring to the reader. Just look at the surrounding context:
"From
a direction that has no name comes
a sound like breathing." He's hearing the reader breathe as they look down at the comic. "The whole continuum tembles
as if cradled." He can feel the reader holding the comic. "And there's a presence, as if I could reach out and touch something immense beyond understanding." He says this as he's
literally reaching out toward the reader in a comic book that was originally released with 3-D effects and 3-D glasses. That was the whole gimmick. Frankly, I'm surprised there's anybody out there who interprets this differently.
The reason people keep commenting about The Writer being "obvious" is because it kind of goes without explaining. If the Overvoid is a paper and the flaw on it is ink, then it seems pretty straight-forward that the ink was drawn onto the paper by a writer rather than spontaneously springing into existence, being drawn by the paper itself, or being drawn by a drawing on the supposedly completely blank paper. This is only further reinforced by Grant Morrison constantly saying it was "drawn on," "written on," etc. He's not trying to say anything complicated here. He's just out-and-out talking about how comics are made, and it's completely in line with his writing style. I don't think 'draw' being in quotes one out of three times in that single article that was linked is particularly good evidence that this is all a metaphor either. First of all, it's only a single instance in a single interview, but secondly, Grant Morrison obviously didn't transcribe that article. The guy who was interviewing him did. Adding quotes around the word "draw" may not necessarily be indicative of Grant Morrison's feelings on the matter. In fact, I'd say it
probably isn't. What we have here is a guy known for constantly inserting metafiction into the core structure of his stories. A guy who constantly goes on about how DC is a real place and Superman is a real character- they just exist in our comics, our art, and our imagination! Then he was put in charge of writing DC's cosmology and creation story. He litters it with metafictional elements everywhere and directly ties it all back to concepts he invented in a previous run that suggest all of DC is drawn on a piece of paper by a group of writers in the real world. He continues to refer to it as a story about ink being put onto paper and stories being drawn on a canvas, wherein the multiverse is the ink/story and the Overvoid is the paper/canvas. It just seems remarkably clean to me. I don't understand the need to try to reinterpret it all as Grant Morrison suggesting that life sprung into the DC by itself and he isn't being metafictional for the first time in his entire career when he calls the Overmonitor "paper" and the multiverse a "drawing" on it.