Well no, that's not the reason why we're not Boltzmann Brains. A Boltzmann Brain is perfectly capable of believing that it is sensing reality in exactly the same way that your brain believes so.
It is worth reading the section "Modern reactions to the Boltzmann brain problem" in the article to understand why the Boltzmann Brain is a useful thought experiment.
It is worth reading the section "Modern reactions to the Boltzmann brain problem" in the article to understand why the Boltzmann Brain is a useful thought experiment.