I think about it along this analogy:

You ring up your artist friend and would really like to see this specific thing drawn. Your friend gets inspired and is happy to oblige completely for free as they make art for fun. You give them specifications, they send you progress pictures and you tell them how to tweak those WIP pictures until you get the piece you envisioned, drawn by this artist friend of yours.

Now, who owns the work? The artist, right? You don’t get to claim ownership just because your instructions got that piece done.