They don’t. To get the probabilities about something occuring in our universe, you need to get the information about our universe first. Solomonoff Induction tells you how to do that, in a random universe. After you get enough evidence to understand the universe, only then you start getting good results.
Yes, but we already have lots of information about our universe. So, making use of all that, if we could start using SI to, say, predict the weather, would its predictions be well-calibrated? (They should be—modern weather predictions are already well-calibrated, and SI is supposed to be better than how we do things now.) That would require that, of all predictions compatible with currently known info, ALL of them would have to occur in EXACT PROPORTION to their bit-length complexity.
Is there any evidence that this is the case?
To my mind all such questions are related to arguments about solipcism, i.e. the notion that even other humans don’t, or may not, have minds/consciousness/qualia. The basic argument is that I can only see behavior (not mind) in anyone other than myself. Most everyone rejects solipsism, but I don’t know if there have actually many very good arguments against it, except that it is morally unappealing (if anyone know of any please point them out). I think the same questions hold regarding emulations, only even more so (at least with other humans we know they are physically similar, suggesting some possibility that they are mentally similar as well—not so with emulations*). Especially, I don’t see how there can ever be empirical evidence that anything is conscious or experiences qualia (or that anything is not conscious!): behavior isn’t strictly relevant, and other minds are non-perceptible. I think this is the most common objection to Turing-tests as a standard, as well.
*Maybe this is the logic of the biological position you mention—essentially, the more something seems like the one thing I know is conscious (me), the more likehood I assign to it also being conscious. Thus other humans > other complex animals > simple animals > other organisms > abiotics.