I studied neuroscience and I agree, this is unlikely to have anything to do with anything. In my view it's much more likely that the speed of processing is due to the brain constantly making predictions - it's an interesting thought experiment to consider the brain as simply a huge prediction machine in various modalities - most of which are pretty accurate, and therefore fast, once you've been alive for a while.

Once you get unexpected outcomes then the speed of thought slows down a lot. I was studying the neurobiology of reading and a good example is the difference in brain activity caused by the two sentences "The jam on the motorway was very slow" and "The jam on the motorway was very sticky" - the first elicits almost no activity, but the second causes a lot more activity because of the unexpected word "sticky" needs to be parsed consciously.

I think it's an issue of scale in some ways. The brain is so complex it's almost impossible to think about it clearly except in very focused studies. There's a lot of deeply methodologically flawed research out there making overly broad claims.