the issue is that right now your mapping is split up in 6 overlapping pieces based on sphere type you picked. basically its mapped like a cube is, so in order to do an unwrap you first have to start with the uv map as one continuous mesh, thats why you need to flat map it first. dont worry about the fact that you are just pancaking the uv map, only after you do this can you do the unwrap steps. the others are right though that a sphere will not unwrap really accurately, but I agree this is good practice for doing a head or something rounded like that.