I've just discovered "Mental Models". It's really weird putting a name to the mechanisms I've used to explain and reason for as long as I can remember.
For a child "I pictured it in my head" is equivalent to an adult saying "I have a mental model of it"
There are many hueristics that are not mental models. There are many things that are frameworks that are not mental models.
Labelling something a "mental model" as used in this context serves the purpose to communicate "here is an abstraction with unusually good power-to-weight ratio that you can leverage to aide your thinking/reasoning about situations that meet a given set of criteria".
It's actually a very specific thing.
One interesting thing about heuristics is that it's important to learn when they _don't_ apply. If a heuristic is true 80% of the time, it's also untrue 20% of the time.
And the obverse to that thought is that you shouldn't let that 20% fail rate discourage you from using the heuristic the other 80% of times.