So you meant something like "counterfactually, it's more likely that Steve Jobs changed his mind about treatment than it is that he didn't get pancreatic cancer."

Yes, exactly.

I feel like phrasing this in terms of quantum mechanics ("the amplitude of outcomes where steve jobs changed his mind etc. etc.) actually makes it more difficult to support.

Yes, I feel like I've opened a can of worms in opening this line of questioning in my brain and now I'll have to think about it for a few hours.