It is less complicated than it looks, once the terms are clear.
The change has been coming for a while, but it only became obvious this year.
The exceptions
Most of the confusion comes from two terms that sound alike and mean different things. The practical effect is easier to see in a single example than in a summary.
Where to go from here
There is a deadline involved, and missing it costs more than the difference. The exceptions matter more than the rule, and there are three of them.
It rewards a little attention now and punishes leaving it to next year.