Why do you think that? A Boltzmann brain will immediately start to degrade but that does not mean there is zero time for thought.
If I were a Boltzmann brain, I would spend most if not all of my existence dwelling, contemplating, ruminating over the things that took me to my current point in space and time. Then I would quickly type something up and post it on a forum to confirm that I
Of this range of possibilities, ones giving you a seemingly coherent and ordered timeline of experiences, or one that is disordered but close enough to order that it can be readily can be interpreted as ordered, would appear to be more improbable.
>on that small of a timescale, your existence is really just a single instantaneous snapshot of a state of mind, and there’s no time to recall a sequence of memories or think through logical propositions.
I think this is very true. Even being around long enough to pose the question to yourself gives you reasonably strong confidence that you've 'tested out' of being a boltzman brain. Though I think that consideration is being momentarily set aside for purposes of this variant of the thought experiment.