Except that the first block and the millionth are not of equal value so there is very definitely a difference in risk when trusting one over the other. The info

Except that the first block and the millionth are not of equal value so there is very definitely a difference in risk when trusting one over the other. The information that the millionth block is safeguarding is way more valuable than the information the first block is guarding. You can't really treat them equivalently.