"Why is fiction fiction? Why is poetry poetry? Why is sculpture sculpture? "Creation story" has a specific meaning and has for a very long time. It's about mythology and religion."
Citation needed. You already group mythology and religion, so clearly the distinction is not between living and dead belief systems. Absent such a distinction, scientific origin stories fit as well as religious ones: Both are accounts of (per Heidegger) "why there is something rather than nothing."
"But it looks like you're being stubborn as well."
In what way?
"I didn't say I'd be mean to the student in any way."
Apart from laughing in her face, you mean?
"I'd try to help him or her understand what creation stories are and the function they have served over the millennia."
Hey Mr. "Fair and Open-Minded," is this before or after you arbitrarily exclude scientific creation accounts?
"They generally are impressed by my open-mindedness, fairness, and desire to present both sides of controversial issues."
Repeat that every night in front of a mirror before bed to keep the bad thoughts away.