The difference is the law allows people to keep NATURALLY SHED antlers they find. The law doesn't not allow for people to keep antlers from deer that were killed by vehicles or that are found dead. It is that way so people don't intentionally kill them just for the antlers.
I know most people wouldn't do that, but there are also plenty who would. I watched guys running them down their big brush guard protected truck one night. Another guy who, after I caught and prosecuted for several bucks he had killed and cut the heads or in many cases just the antlers off of, admitted that he had killed 34 bucks for their antlers in the two or three weeks before I caught him. He also told me that the guy he learned it from typically killed around a hundred bucks per year just for the antlers. There is no question in my mind that people of that mindset would think nothing of shooting big bucks just so they could go back later, claim they found it dead and recover the antlers.
The way this law is written it is unlawful for ANYONE to keep antlers from a deer or elk unless they were naturally shed. Naturally shed antlers are discarded by an animal that is still alive and ready produce a new set of antlers the next year so there is not threat to the future of our wildlife resources when someone takes a natural shed antler home.