Why? The time passed for the Boltzmann Brain won’t necessarily be tied to its real frame of existence i think, it may simulate any timeframe imaginable, depending on its starting conditions.
In fact the simulation of any timeframe would be constrained by physical laws.
For example for a Boltzmann Brain with a similar chemical composition as ours the speed at which chemical reactions occur would limit the speed of experience.
For a Boltzmann Brain that simulates ours with a very different physical substrate the speed of light would still be a limit.
For example for a Boltzmann Brain with a similar chemical composition as ours the speed at which chemical reactions occur would limit the speed of experience.
For a Boltzmann Brain that simulates ours with a very different physical substrate the speed of light would still be a limit.