Well it is a new system that doesn't allow people to be grandfathered in, but unless we get clarification from @TeamYouTube then I don't know what to expect a year from now if i manage to reach 4000 watch hours, and then the following I get 3999.
You're right. Surely it is in a way supposed to make people work for it, and put in the effort to reap a reward from a platform like this. It's not really something I can complain about.