This analogy seems to me rather to suggest that our ontology likely has limits that we cannot conceive of. After all, if the dog was able to formulate the thought, he would probably also describe his ontology as "maximal."
As support for this --would you describe the ontology of a human being in a hunter-gatherer tribe ten thousand years ago as maximal? It would rather seem that the human ontology has expanding significantly several times since then. What makes How can you be sure sure that process has achieved a final terminus?