Small changes add up faster than most people expect.
The change has been coming for a while, but it only became obvious this year.
The exceptions
The practical effect is easier to see in a single example than in a summary. The exceptions matter more than the rule, and there are three of them.
What it costs
There is a deadline involved, and missing it costs more than the difference. Nobody is required to explain this to you, which is half the problem.
It rewards a little attention now and punishes leaving it to next year.