I can't speak for government. But speaking for industry—not that I'm mandated necessarily to represent any companies—when you come to me and say I have to reduce my emissions 6% below my 1990 baseline or 25% below my 1990 baseline or 10% below my 2000 baseline, the first thing I do to figure out what that means to me is say, “What does that number equal relative to my current emissions?” Anyone in the private sector trying to respond is always converting whatever standard you are proposing to a standard relative to the most recent year for which they have reasonable estimates for their own operations.
I don't know what government's motivation is to go to a recent-year baseline, but that's a practical way to represent the requirements you're imposing or asking us to deliver to. That's completely separate from how you'd pick those targets.