If we had, there would be no reason to train a model with more parameters than are strictly necessary to represent the space's semantic structure. But then it should be impossible for distilled models with less parameters to come close to the performance of the original model.
Yet this is what happens - the distilled or quantized models often come very close to the original model.
So I think there are still many low-hanging fruits to pick.
We do understand how they work, we just have not optimised their usage.
For example someone who has a good general understanding of how an ICE or EV car works. Even if the user interface is very unfamiliar, they can figure out how to drive any car within a couple of minutes.
But that does not mean they can race a car, drift a car or drive a car on challenging terrain even if the car is physically capable of all these things.
For example if I ask "If I have two foxes and I take away one, how many foxes do I have?" I reckon attention has been hijacked to essentially highlight the "if I have x and take away y then z" portion of the query to connect to a learned sequence from readily available training data (apparently the whole damn Internet) where there are plenty of examples of said math question trope, just using some other object type than foxes.
I think we could probably prove it by tracing the hyperdimensional space the model exists in and ask it variants of the same question/find hotspots in that space that would indicate it's using those same sequences (with attention branching off to ensure it replies with the correct object type that was referenced).