Again you are assuming the numeral one refers to person without establishing that.
What if I said, God has only one attribute because I'm a monotheist.
You say, "What? How does that follow?"
I answer "It's right in the name, silly—MONOtheist. He can only have one attribute, duh. It's right there, God is ONE."
See, the one does not refer to attributes—so there are senses in which God is NOT one for both of us.
Your God is not one! What? One what? One attribute! Well... no, he's not. He has multiple attributes.
That is exactly what your logic will sound like to me.