My library had a book entirely about exploring comic creation through the medium of a comic book. Things like finding a wall too long to go around, and noting that the reader only knows this because of the dialogue highlighting it, since the wall can only be as big as the panel. It strikes me as similar.

“Ontological metalepsis”, maybe with some “reification”?

Metalepsis A crossing between narrative levels. Here, a non-physical comic convention becomes physically active inside the story.

Ontological metalepsis A stronger, more precise form: something from one “reality level” enters another. The speech bubble moves from the reader-facing graphic layer into the character’s physical world.

Reification Treating something abstract, symbolic, or conventional as if it were a concrete object. The speech bubble is “reified” because it becomes a usable physical thing.

I love this comic.