It certainly is saying something about ultimacy and uniqueness. Good is a value, God is so valuable in this regard as to be alone on his playing field. There is God and nothing else when it comes to plumbing the depths of that value, good. It is not said here that God is good because, or in relation to: God himself is what good is, period. So to know if something is good, lay it beside God and compare, how does it measure up to the standard.
Sometimes I think we frame our conceptions of God's virtues in the wrong way in order to "prove" that God is good (i.e. God could never do this or that, or God can not do this or that), but God does whatever he wants and there is no power in heaven or earth that can make him do other. Whatever he says or whatever he does is the very definition of good, it is the standard. He is the standard, and it is left for us to trust him.
The question of contigencies with God is inconsequential. Whether he would have or could have done something else, something better, something more or even less good, is a complete abstraction. We have what's he's said and done and that's it. Is it really possible to imagine another course for the omniscient and omnipotent? I don't have a brain that operates in that realm, does anyone? Of what value or reliability could our musings be?
I believe that good and evil and the option to do one or the other come into play only in the interaction between God and other beings having the power to will. Really, the existence of evil proves the existence of freewill! Evil only exists where a will opposing God's can be expressed, for evil is only evil because it is will expressed in opposition to his. Evil is not an independent, universal value and will not exist in eternity, it's really nothing but a passing vanity.