You say that one can change A by changing B, while there is no causal mechanism by which B can influence A. That's denying causality.
That's finding a loophole in causality, and the distinction is certainly worth making. The DA is only a product of perspective; it isn't a 'real' thing that exists.
Whether the distinction is worth making or not, it is irrelevant to my point, since both are very unlikely and therefore require much more evidence than we have now.
I assume that your idea is to prevent doomsday or make it less likely. If not, why bother with all these simulations?
A self-modifying AI is built to serve humanity. The builders know, of course, that this is much riskier than it seems, because its success would render their own observations extremely rare. To solve the problem, they direct the AI to create billions of simulated humanities in the hope that this will serve as a Schelling point to them, and make their own universe almost certainly simulated.
Plausible?