All of the changes look to be for combating cheating (a very good goal and highly desired by the math competition community), but it seems like the move towards the chosen test centers has created a "minimum 13 years of age" rule
This is crushing for young US students interested in math (and possibly a negative long term effect on high end US math education). There's lots of kids that get started, develop a passion before 13, and this will kill some of their motivation.
Even if they don't want to find a testing center that allows younger participants, maybe at least hold a second "paper AIME" that doesn't apply for USA(J)MO qualification, could be a week later too.