In case of BB the answer (in my opinion) is that if you are in BB your thoughts are random and not casually connected with your experiences, and half of BB thinks that their universe is streamlined, even if it is not. So in case of BB the fact that you think that your universe is streamlined is not evidence that you are not BB.
In case of more conventional simulations, their creators probably tried to create illusion of real world. So they create more or less streamlined universe (and may edit our thoughts if we find holes).
I had just the same topic discussion recently about Bolzmann brains. (here: http://lesswrong.com/lw/17d/forcing_anthropics_boltzmann_brains/)
In case of BB the answer (in my opinion) is that if you are in BB your thoughts are random and not casually connected with your experiences, and half of BB thinks that their universe is streamlined, even if it is not. So in case of BB the fact that you think that your universe is streamlined is not evidence that you are not BB.
In case of more conventional simulations, their creators probably tried to create illusion of real world. So they create more or less streamlined universe (and may edit our thoughts if we find holes).