Hold up here. I get that what was written is from a secondary person. Someone is saying "and God spoke these words.". But that does not make what God spoke irrelevant or untrue or even not real. People quoted Jesus all the time and we don't claim that what Jesus said was not what he said. We trust that's what he said.
The language here is God speaking. Take a look at what God says.
I am the Lord your God who brought you out of Egypt, out of the house of slavery.You must have no other gods before me.Do not make an idol for yourself—no form whatsoever—of anything in the sky above or on the earth below or in the waters under the earth.Do not bow down to them or worship them, because I, the Lord your God, am a passionate God. I punish children for their parents’ sins even to the third and fourth generations of those who hate me.But I am loyal and gracious to the thousandth generation of those who love me and keep my commandments.Do not use the Lord your God’s name as if it were of no significance; the Lord won’t forgive anyone who uses his name that way.Remember the Sabbath day and treat it as holy.Six days you may work and do all your tasks,but the seventh day is a Sabbath to the Lord your God. Do not do any work on it—not you, your sons or daughters, your male or female servants, your animals, or the immigrant who is living with you.Because the Lord made the heavens and the earth, the sea, and everything that is in them in six days, but rested on the seventh day. That is why the Lord blessed the Sabbath day and made it holy.Honor your father and your mother so that your life will be long on the fertile land that the Lord your God is giving you. - Exodus 20:2-12
Bible Gateway passage: Exodus 20:2-12 - Common English Bible
I am the Lord your God. Refers to himself. Now look at other places where he uses or talks in a third person. Do not use the Lord's name in vain. He does not say"do not use my name in vain.". If we were to accept the thought that third person means God isn't speaking then this verse is meaningless and probably the whole command was made up by the writer and not given by God. The same thing goes for the Sabbath Day command. It too would have to have been made up by the writer and not given by God. Same goes for honoring your mother and father.
See the logical conclusion is that if there is a change in person then the writer is speaking and not God which invalidates many of the commands.
Does God ever speak that way other than here? Is this so unusual for God to speak that way? No it is not. There are other places is scripture where God uses third person to speak of himself. In fact Jesus does the same. Remember Jesus said "the son of man has no where to lay his head"? He didn't say "I have no where to lay my head.". But we all accept it as a quote from him. Look up other passages where God or Jesus speaks in third person.
Here is just one.
The Lord said to him, “Go down, and bring Aaron back up with you. But the priests and the people must not break through and come up to the Lord. Otherwise, the Lord will break loose against them.” - Exodus 19:24
Bible Gateway passage: Exodus 19:24 - Common English Bible
Note he dies not say and I will break loose against them. He talks about himself in third person.
This whole idea is just another excuse for those who do not want to take the bible for what it says and accept that God created just as he claimed.