There's optimization left, but no where near as much as the X1. You can harp on HUMA or the fact that its a custom APU but at the same time the APU is closer to a mainline AMD APU than the X1 (due to ESRAM and the fact MS designed large parts of the chip themselves vs Sony just using already established designs).
It's like saying, the OG Xbox has optimization left at the beginning of that gen. Yes, yes it does. But the PS2 used super customized hardware, it has a lot more to do optimization wise.