Ya, I get the reasoning. And I agree with your analysis about the negative consequences. But the part I actually think is weird/complex is the way it ties tax

Ya, I get the reasoning. And I agree with your analysis about the negative consequences. But the part I actually think is weird/complex is the way it ties tax returns together from adjacent years. For my 2015 federal return I don't deduct my state taxes on my 2015 income, I deduct state taxes I paid in 2015. Those can be two different things. I just find that a bit weird.