This is not a good argument. Natural systems, the subject of neuroscience/psychology, are much harder to analyze than artificial systems. For example, it's really difficult to study atmospheric gases and figure out Boyle's/Charles law. But put a gas in a closed chamber and change pressure or temperature and these laws are trivially apparent.
LLMs are much more legible systems than animal brains, and they are amenable to experiment. So, it is much more likely that we will be able to identify what "reasoning" is by studying these systems than animal brains.
P.S. Don't think we are there yet, as much as internet commentators might assert.
