I think I don’t understand what makes you say that anthropic reasoning requires “reasoning from a perspective that is impartial to any moment”. The way I think about this is the following:
If I imagine how an omnitemporal, omniscient being would see me, I imagine they would see me as a randomly selected sample from all humans, past present and future (which don’t really exist for the being).
From my point of view, it does feel weird to say that “I’m a randomly selected sample”, but I certainly don’t feel like there is anything special about the year I was born. This, combined with the fact that I’m obviously human, is just a from-my-point-of-view way of saying the same thing. I’m a human and I have no reason to belive the year I was born is special == I’m a human whose birth year is a sample randomly taken from the population of all possible humans.
What changes when you switch perspectives is just the words, not the point. I guess you’re thinking about this differently? Do you think you can state where we’re disagreeing?
Huge success!