>However, I think the article still makes a strong point, which is that neuroscientists use many experimental and signal-processing techniques whose utility hasn't even been demonstrated in principle, much less in practice.

This is the point. There are multiple levels of interpretation layered on top of the physical process. There is no reason to believe that they are tidy or hierarchical either, abstractions and indirections can leak left and right (or top to bottom). We lack the language and tools to describe these structures laid bare, and words like "abstraction" and "indirection" are probably a bad fit. Even "interpretation" might prove to be conceptually misleading when cracking this nut, so to speak.