It does get at your question, in that I am claiming that any formulation of quantum mechanics must have these rules in some form. So I would say that your desire to find a way to describe MWI branches that doesn't have this feature is equivalent to wanting quantum mechanics without interference, and is therefore hopeless.

The canon is that the feature I am describing is indeed hopeless -- that indeed the Born rule is inconsistent with a uniform counting measure. This I accept more or less as fact. But my question is about demonstrating this directly, but simply evolving a wave packing, counting the "worlds" and showing that the principle of indifference leads to a different probability than Born. What you are showing is distinct from this, and much more obscure.

That would be fine if it were the only possibility, but I don't think it is, in that in principle it seems clear that such an example should exist, hence my original SE question: what is an example where you evolve a wave function into unequal probabilities that directly demonstrates this difficulty.

Interference (well linear superposition in general) is perfectly compatible by itself with MWI; it is taken as an axiom with the total superposed amplitude describing "world density" (BTW this isn't necessarily an unmotivated ontology, it is simply taken as isomorphic to a mathematical description of many classical trajectories). The question is, given this amplitude, interference contributing to it or not, do the amplitudes imply Born probabilities given a uniform measure?