Could you explain just what God's intention was (is?), since you seem to know? And do you see this intention as superior to the "natural biological design" you mention? Or are you just confused?
No, actually you are confused.
They are one and the same.
The natural biological design reflects God's created intent for human sexuality, because this design IS God's creation.
And this design/intent couldn't be much more evident. It's male-female.