A plain look at what changed, and what it means from here.
It is the sort of thing that seems settled until you look at the detail.
What actually changed
Most of the confusion comes from two terms that sound alike and mean different things. The exceptions matter more than the rule, and there are three of them.
What to check first
The exceptions matter more than the rule, and there are three of them. The practical effect is easier to see in a single example than in a summary.
It rewards a little attention now and punishes leaving it to next year.