I don’t see the distinction between what God says and ultimate moral truth, because God is Truth. God is also Morality, and Love, Justice, Peace, Strength, Life, etc… In my mind, that doesn’t limit Him because ultimately they’re all the same thing. They’re all God. I’m not saying that God is not a person (3 Persons actually) or that He’s just a collection of virtues. He’s the embodiment of those virtues in personal form. So our words are limited, and our concept of true morality may be limited, but God’s reality as embodiment of true morality is unlimited.
So when God says “x is moral, y is immoral”…it’s just a reflection of His nature. He never sat down and decided which things would be moral or immoral, IOW.