The triangle example doesn't prove it because our predictive model could also say "hey, things don't just change color and shape like that, they need to move". It's similar to how an LLM can be more accurate with math when asked to step through and reason through it's logic - by stepping through the individual steps it can create a larger system.
The thing that made me question if a "mental model" is at the base of human cognition - people who do those memory competitions, the clear winning strategy is the memory palace, or imagining walking through a house where each room is another number - they have to build step by step memory, it's not like an SQL database where they can just SELECT from random. Another one was the insight from GTD that if you remember 7 things to do, you're always repeating those 7 things to yourself to keep them in active memory.
There's a strong argument that the mental model is derivative of a predictive model in the human brain, and we can just appear to have a mental model since we have an internal dialogue that runs so fast in the background that even we rarely recognize it. (anyone who has kept a steady meditation or similar practice should be familiar with it)