What I have had physics PHD friends explain to me is that the 'wave' evolves completely deterministically. The way they see it, measurement is just 'getting entangled with the wider world, thus concentrating the wave function'.

Almost everything we interact with has this concentrated wave function. And when you see something without this concentration the process of how it 'decoheres' is chaotic. It just turns out that the chance of concentrating in a spot is proportional to the wave self-conjugation.

I could imagine the idea 'almost everything is engangled' meaning the chaotic nature of this concentration process is essentially perfectly random. Since you'd be interacting with trillions of other waves.

Do I understand correctly that you're claiming it's "at least exponentially unlikely" (so to speak) for a fully-deterministic-since-the-Big-Bang model to result in a superdeterministic world? Or to rephrase, something along the lines of: "a vanishingly small set of evolution trajectories from a fully-deterministic-since-the-Big-Bang would result in a superdeterministic world that would explain ours"?

No, I wasn't talking about superdeterminism at all.

My point is that the evolution of the waveform is deterministic. Waveform collapse is where lots of theories introduce indeterminism. I propose a theory in which waveform collapse is technically deterministic.

My proposition is that the process is deterministic but chaotic. With the simultaneous state of all other particles determining how this collapse happens. Making it deterministic, but truly impossible to predict without a picture perfect representation of the outcome.