You need to read ahead to chapter 33 which preceeds the second tables of stone:
And it shall come to pass, while my glory passeth by, that I will put thee in a clift of the rock, and will cover thee with my hand while I pass by: And I will take away mine hand, and thou shalt see my back parts: but my face shall not be seen. (Exodus 33:22,23)
However, that has little to do with the issue at hand
I think it is precisely the issue. People do not recognize that Jesus Christ is God; and that it was he who spoke the Law to Moses; and that he will judge the unbelieving at the great white throne using his law which is eternal.
You make a good point: The three are one, therefore Jesus did speak to the issue. Thank you for your patience.