"Should be describable" is a false metric. We can hear differences between categories and not be able to verbalize what we're hearing. It's the same for anything -- you could walk through a museum showing abstract expressionism and action painting, and feel that one of the styles speaks to you, and yet not be able to put into words how the two styles are different.
The brain can categorize much more easily than it can create a concrete definition for those categories.
> We can hear differences between categories and not be able to verbalize what we're hearing. It's the same for anything
For some reason, the view is widely held that internal thoughts are expressed in words. This would mean that anything you can think can easily be verbalized.
The fact that this view is quite obviously false seems to bother very few people.
The brain can categorize much more easily than it can create a concrete definition for those categories.