Basically if your evolution fitness only depends on perceiving some sensory input that's in a certain range, you're only going to evolve to see that input that falls within that range. You can 'see' only the range of visible light, because that's all that was useful to us when we were evolving. There's everything from microwaves to radio waves that are also floating around, and we can't perceive them at all.

I think if we were utterly reliant on our senses to perceive reality, this would be a good argument in favor of realities ultimate inaccessibility. But we can actually reach beyond our natural senses to see things like microwaves and radiowaves.

The question is now: What else is out there that we haven't been evolved to perceive? In a way, most of the really useful science of the past several centuries have been finding new ways to discover those aspects of reality that are hidden to our primitive primate brains.

The argument he's making isn't about 'philosophical reality' as much as it's about conscious reality.