The word "model" is another of those words that Minsky called "suitcase words"--- they can be used to mean many things. I don't think Marcus is saying that that LLMs have "no model", just that they don't have a model of the type that a symbolic system could have. He gives many examples of deductions that a symbolic AI system can easily do, which GPT-3 is simply incapable of.
It seems clear to me that if the CLIP-like part of Imagen or Stable Diffusion can take an image made of pixels and yield "cat" and similarly take "dog" and produce a 3D neural radiance field that we can light just like any other 3D model and recognize as a dog then there must be an accurate and useful model of both how vision works and what dogs look like and the English relationship between those two things inside the machine.
I also wish Gary Marcus was replying to Google's Minerva paper instead of GPT-3. The ability to answer multi-step symbolic problems is basically here. https://ai.googleblog.com/2022/06/minerva-solving-quantitati...
I'd also note that decades of attempts at automated theorem proving with symbolic systems haven't yielded similarly impressive results. Now we have deep learning models helping with proof search.