That's a fascinating philosophical presupposition you have there: That there is such a thing as a difference between the observable* behavior of a system and its real* behavior. I won't agree or disagree with you. Just pointing it out because it's really interesting to me.
*You used essentially those words ('observer', 'really'). I won't try to pin you down into a particular definition of them, but I'm guessing we at least approximately agree on what they mean.
You could make a similar but less controversial statement by substituting "low-fidelity observer" & "high-fidelity observer" for "observer" & "reality". I wonder if that's what you mean, or if you meant what you said?
Hm... I suppose this could be mathematically/logically equivalent, but the thing that bugs me in GP's answer (and the way I hear QM talked about in general) is the very concept of an observer. I've never heard a good explanation of why an observer would be a thing - I'm not sure if there could be, without creating some kind of magical realm for it to live in, detached from the rest of physics.
What "an observer" really means, in the context of QM, is a large, approximately classical system interacting weakly with the system being "observed" (such that the interaction can be modeled perturbatively). Humans "observe" photons, but so does a pail of water.
It's a way of framing certain classes of problems, not a distinct sort of entity.
*You used essentially those words ('observer', 'really'). I won't try to pin you down into a particular definition of them, but I'm guessing we at least approximately agree on what they mean.
You could make a similar but less controversial statement by substituting "low-fidelity observer" & "high-fidelity observer" for "observer" & "reality". I wonder if that's what you mean, or if you meant what you said?