The answer lies in the text itself:So, you say that when Jesus quoted the shema, he was thinking of 'neither of a "deitific nature" or "a person", but "two persons" ---- He and the Father in perfect unity.
But you agree that the scribe thought that Jesus was speaking about the Father only as being the subject of the shema.
If this be the case, why did Jesus consider him to have answered "wisely" and why did he commend him for his comprehension of his words? Would this not be confusing and misleading if - as you say - the scribe had misinterpreted Jesus' words?
And the scribe said to him, "You are right, Teacher; you have truly said that he is one, and there is no other but he; and to love him with all the heart, and with all the understanding, and with all the strength, and to love one’s neighbour as oneself, is much more than all whole burnt offerings and sacrifices."
And when Jesus saw that he answered wisely, he said to him, "You are not far from the kingdom of God." Mark 12:32-34
The scribe's "wise" answer is found in the bolded words, and not in the fact that he thought Yahweh was a single individual (as did all the scribes and pharisees of the time).
Consider the rest of Jesus' reply to the scribe. "You are not far from the kingdom of God." Which do you think indicates that the scribe was not far from the kingdom of God? ----- the fact that he said that to love God completely, and one's neighbour as oneself is much more that the totality of burnt offerings and sacrifices? ----- or the fact that the scribe thought that Yahweh was a single individual?