It's nice when a question about the new system is raised and can be easily answered.
As regards the ML 12 restriction being there a week ago: It wasn't.
If it helps, this additional restriction doesn't actually address any of the issues that I had with other enhancement abilities. The fact that racial enhancements are effectively wasted and there is no concept of "class AP spend" and only "tree AP spend", doesn't do anything to relax the overly restrictive constraints on builds as I see them.