This does not understand the content of the argument of Yudkowsky’s post.
It doesn’t rely on sampling from a collection of observers throughout the universe: the problem remains without that framing.
Let’s put it like this. Right now, you have the memory of being in an ordered universe, but you’re considering Boltzmann-Schutz brains and feeling a bit woozy. You decide to perform an experiment: you’ll wait fifteen seconds. If your experience dissolves into chaos, Boltzmann brains made a correct prediction. If it doesn’t, they made an incorrect prediction.
After performing the experiment, you get the non-Boltzmann brain result, and this experiment is very well-replicated. So any theory of physics must account for this, even a theory of physics like “all possible observers are instantiated.”
As in the example that Yudkowsky recounts from Feynman, a system of labeled gas particles in a box which instantiates all microstates with uniform probability does not instantiate all macrostates with equal probability. Ones which are more well-mixed are exponentially more common. This a wide-ranging phenomenon: see also the Central Limit Theorem.
The problem isn’t with whether all possible observers are instantiated, but how many or how much they are instantiated. In an eternal classical fixed-size universe at thermal equilibrium, most versions of you will immediately dissolve into chaos five seconds from now. Similarly, most Earths aren’t in a galaxy, they’re in a chaotic sea.
Being a halfer in the Sleeping Beauty problem does not fix this.
The situation is more analogous to the following: A fair coin is flipped. If it lands heads, nothing happens. If it lands tails, an extremely biased towards tails coin is flipped. If that coin lands tails, you are killed. If that coin lands heads, nothing further happens.
The event occurs, and you observe you are still alive. What is the probability the coin landed heads? Very high, and this can be worked out with the usual conditional probability math. The post you linked makes this very point, connecting Sleeping Beauty to the boy-or-girl paradox.
This is amazing.