sorry venerable, not missed on my side. This is how I understand this:
“Brahmin, if I had not given up defilements I might have become a god … a fairy … a native spirit … or a human. But I have given up those defilements, cut them off at the root, made them like a palm stump, obliterated them so they are unable to arise in the future.
obviously he is not talking here as if he had died and then been reborn like a Buddha. He taught how Reality arise to us moment after moment, and all beings arise and experience their reality according defilements. The reality we experience now is in our present way because defilements. Experience of reality is conditioned by ignorance and defilements, and it include the present perception of body, mind and rest of reality.
Suppose there was a blue water lily, or a pink or white lotus. Though it sprouted and grew in the water, it would rise up above the water and stand with no water clinging to it. In the same way, though I was born and grew up in the world, I live having mastered the world, and the world does not cling to me.
He says he doesn’t belong to the world or to the realm of human beings never more. And finally, the Buddha again says He shouldn’t be identified as a human being. Buddha said he should be identified only as a Buddha.
According texts, the Buddha was free of ignorance and he could know and perceive what we cannot. He could perceive all the beings and worlds. Also, the Buddha was perceived by other beings (gods, devas, humans…) in the way he wished.
Also according texts, we know the human beings perceived a human body when they grasped the Buddha, while some gods perceive Him in invisibility or not. And some devas perceived Him like a being extremely radiant.
Reviewing these facts, obviously we are not talking about a human being. A Buddha is a different thing.
If we accept the experience of Reality (and of ourselves) being conditioned by ignorance and defilements, the “human being” also is an experience conditioned moment after moment. And it seems to me unavoidable to understand that the human being was Siddharta but the Buddha was not a human being never more. This is supported by his own words:
Remember me, brahmin, as a Buddha .
this is how I understand “No, I’m not a human being”.
well, we are many thousands and I suppose every person has his own understanding of what can be a Buddha. It can be a personal issue.