I do notice that the feat requirements are specific to the chosen weapon group. So, for example, my fighter specializes in axes and the feat requirements specifically say weapon focus slash (for one and two handed melee axes) or weapon focus thrown (for throwing axes). So it might be the case that the feat requirements don't appear until you actually select the enhancement or maybe the initial weapon group. I don't know, I'm not going to bother resetting my enhancements to find out. But they do require the feats.