There is no need for a conscious observer in any quantum phenomena - the universe worked the same way before humans evolved, and before any other life evolved. It will continue to function in the same way when life on Earth is gone.
And any naturally occurring examples of the double slit phenomenon will continue to function in the same way no matter what happens to humans.
The myth that we are necessary for the universe to function grew out of the observation that we can’t identify both the position and speed of an electron or anything else at that small scale - we can make either measurement, but one precludes the other. That is a comment about measurement, not about human consciousness, though. Or any kind of consciousness.
The moon is not a wave function that only collapses into a physical moon when someone sees it - and yes, I have heard people make that claim.
And, on topic - the outcome of bayesian statistical analysis depends on your assumptions going into it. The probabilities you assign to different parts of the analysis, in this case, are arbitrary. We can’t, literally, conceive of what an intelligence capable of simulating the observable universe would be like. Our brains are not sufficiently complex (by many orders of magnitude) to do that. The “research” authors are applying human 21st century concepts and assumptions to a potential situation that is more complex than we can ever come close to understanding.
Contemplate the last segment of your right little finger. Biologists and physicists are a long, long way away from fully understanding what goes on in that small part of your body over the course of your life - or even from one instant to the next. It contains a multitude of mysteries that we currently can’t even identify, much less unravel; just creating the tools capable of doing so will take decades of tool building iteration. At our current primitive technological stage, good luck trying to prove we are or aren’t in a simulation of the universe.
While human arrogance is nearly infinite, our intelligence is very limited.