Rather than be so quick to label heretics, read more carefully. He stated that God is plural. God the father, God the Son, and God the Spirit. The Son restricted his nature to become flesh. Yes, he was both God and man as I know the author would also attest. But if scripture tells us something, it's better to listen than to start spouting false labels.
Hebrews 2:7 Thou madest him a little lower than the angels; thou crownedst him with glory and honour, and didst set him over the works of thy hands: 8 Thou hast put all things in subjection under his feet. For in that he put all in subjection under him, he left nothing that is not put under him. But now we see not yet all things put under him. 9 But we see Jesus, who was made a little lower than the angels for the suffering of death, crowned with glory and honour; that he by the grace of God should taste death for every man.
Jesus is God. Jesus was made 'lower than the angels'. Therefore God restricts his nature. It's really not that hard to understand when you take the time to follow reasoning.
"The Son restricted his nature to become flesh."
God does not reduce His nature. The nature of the Godhead remains unchanged! Your explanation would have me believe that when Jesus became a man, the Holy Spirit and the Father lose power because the nature of God is now restricted! Remember, Jesus is only One of the Three Persons of the Trinity that utilize the Divine Nature.
It would be better to say that Jesus did not display His divinity fully while He was Jesus of Nazareth. His full divinity was "hidden" from the Apostles and Jews. Because the Person of Jesus Christ is wrapped in mystery, we must be careful on our definitions.
Jesus being a little lower than angels merely means that He took on the nature of a man. Being that God is impassible, that is the only way Jesus could suffer and die, by taking on our nature. This is what the author of Hebrews refers to - that the Logos, the pre-existing Second Person of the Trinity took on the nature of man, IN ADDITION to His nature already as God. Both subsist in the person we call Jesus Christ. As Christians, we must be careful on such explanations, as they lead to un-Biblical ideas. We must believe that God became Jesus, fully God and fully man.
Regards