I didn't say whether it's reincarnation or not. However, the reincarnation theory couldn't be ruled out because at this point, unlike in the book, MY's had died.
Another possibility, TTJ was not a reincarnation, but was born with MY's face. This is because, in the flashback, this ancient demon god didn't look like TTJ. Idk why it's important for him to show TTJ's face to MY. Probably, he just trolled MY out of spite by creating a vessel that looked like MY. It could be that MY saw a stranger's face, but it could also be that it was MY's face. This is just a theory.
One thing for sure is that Ji Ze and MY (probably Chun Huang also) made a self fulfilled prophecy, because the dream had been arranged beforehand. When Susu entered the dream, Ji Ze and Chun Huang even reminded her of her mission. It likely that Ji Ze, the god of time, had read the future and, together with MY, took a precautionary measures.
MY in the book just wanted to share his story. Hopefully, the younglings would take an inspiration. However, MY in the drama was fulfilling his duty to protect the world. He gave Susu the tears, but secretly unwilling to let her use it. Eventually, it was MY's scale that protected TTJ from the nails.