This is weird and in my opinion f2pool is trying to do some experiment as to what kind of core they will eventually use in their system. My friends made a joke about that and told me that f2pool will accept all those codes at once, they will divide the pool in different categories so they can accommodate all kind of miners who uses different kind of codes. I just simply told him that it is impossible to happen and probably later on they will post that kind of code will they support.