The short version, for anyone who has not been following closely.
The change has been coming for a while, but it only became obvious this year.
The exceptions
There is a deadline involved, and missing it costs more than the difference. The figures move about, but the direction has been the same for three years.
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.
Whatever you decide, write down why. The reasoning is the part you forget.