I don’t see why something would need to be entirely coherent to be useful. If you have a program which, when given a statement, assigns a value between 0 and 1, to be interpreted as if it were a probability of the statement being true, it needn’t define an entirely coherent probability distribution.

Human perception is coherent because it tends to accurately model the physical world from which it's constructed, by means of sensory input and memory, and if this were not the case, we would have gone extinct as a species ages ago. While it is true that the model of human perception isn't perfect, it would be incorrect to call it incoherent to the same or similar degree as the incoherence demostrated by LLMs, as jmole's earlier comment implies.

Even if one must consider the model of human perception incoherent, one must also consider it vastly more coherent than whatever LLMs model reality on, if anything.