But each variant of a boltzman brain that accounts for the passage of time, passes that 'test' at the cost of being less probable overall. Most boltzman brains won't pass that test, but some will. And then you throw in the other tests people have mentioned: a feeling that your memories are somehow internally coherent and consistent. Most won't pass that test either, but some will. And 'some' could be so many that, if you were picking out of a hat, they are still more likely than that your experiences have really happened.
I guess the interesting question is whether you can collect together enough 'tests' that filter out BBs, that you can pare down the range of possible BBs that pass the tests, to the point that they become a less probable explanation than the actual spontaneous emergence of life in the universe.
And of course probability doesn't matter for events that occur only once in the universe. This isn't a scientific theory.
And if we've thrown that core reference frame out the window we've stepped entirely outside of the rules that are the basic structure of the whole boltzman brain thought experiment.
In other words, take a real human considering whether they are a Boltzmann brain and deciding that they are not. Any single moment in that human's existence can be simulated by a Boltzmann brain existing momentarily, including the moment where the human concludes that they are a real human, and the moment where the human reflects on its conclusion that it is not a Boltzmann brain.