we would still be constantly pruned back to the CEV of 2045 humans
Two connotational objections: 1) I don't think that "constantly pruned back" is an appropriate metaphor for "getting everything you have ever desired". The only thing that would prevent us from doing X would be the fact that after reflection we love non-X. 2) The extrapolated 2045 humans would be probably as different from the real 2045 humans, as the 2045 humans are different from the MINUS 2045 humans.
I wonder if the FAI will be sad to not be able to see what evolution in its unlimited ignorance would have come up with for us?
Sad? Why, unless we program it to be? Also, with superior recursively self-improving intelligence it could probably make a good estimate of what would have happened in an alternative reality where all AIs are magically destroyed. But such estimate would most likely be a probability distribution of many different possibilities, not one specific goal.
I'm dubious about the extrapolation-- the universe is more complex than the AI, and the AI may not be able to model how our values would change as a result of unmediated choices and experiense.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.