Takumi Oil, SN/GF-4

[tinmanSC]

I was looking at Takumi Oil's page. And on their home page (if you can read Japanese) they have a 0w-20 oil that is SN rated, but is GF-4, not GF-5. I didn't think this was possible. I thought all SN oils were GF-5. I guess I don't understand the specs well enough if this is true. SN and GF-4/5 are independent specifications?