What is the unconstructed? You said "he appeared in the form of a man." Does that mean you believe he was not a man?
Ah this is a complex subject and it goes into the nature of Nirvana.
The unconstructed means simply that paradoxical nature that escapes all forms and human definitions. That great unspeakable that the Buddha acknowledged was there since it is one and the same with Nirvana, but refused to say anything about.
The Buddha entered Nirvana at his death. Even so, Buddhists have continued asking him and all the Buddhas for help, appealing to his great heart of pity for all suffering creatures. Nirvana is not extinction in traditional Buddhism. It's not something we say much about, however.
As to the Buddha being a man, certainly he was born as one and lived. However, he wasn't like other men. He had auspicious birthmarks on his body and was born to become the Buddha.
Nothing could have prevented that destiny. Once he became enlightened he claimed to be neither god or human, but Buddha (awake).
He had knowledge and abilities through his enlightenment most of us don't have.
In the sense Mahayanists have believed that Shakyamuni descended from the Pure Land of the Buddhas and was born a man for the salvation of beings- it has been held he was more than human.
Historically Buddhists have always treated it of such fundamental importance that the Buddha was not just an ordinary man that texts like the Parinirvana Sutra (part of the canon of both vehicles- Theravada: Parinibbana Sutta) anathemize anyone who would say so, or deny the Buddhas manifest from the Ultimate.
