Interpreting "the letter of the law", it sounds okay if the app wasn't for a practice performance task.
Going with "the spirit of the law", I agree with you an important factor is whether the student received feedback (and in this case it seems the student hasn't received feedback from you, so no red flags there). I would also make sure the student hadn't collaborated with anyone in creating the original code (and obviously not plagiarized). I could see it as the student starting the Create Task outside (before) the dedicated class time, so all other Create Task rules would have to apply to that code.
Overall, I'd say it's still iffy since I wouldn't encourage my students to do it, but if my student did follow all those rules and decided to use the code, I don't see any reason I'd be obligated to flag them as plagiarizing and I don't see how that breaks any of the rules.