I'd have to agree. And honestly, even if the kid didn't admit to using AI, if they were using AI as a source and not citing it, then it was a failing paper regardless, as certainly one of the requirements was to cite sources.

If I was handling this, I'd treat it the same as if somebody just copy pasted some text off Google search and didn't cite. I'm not sure I'd give the student a 0. But it wouldn't be a good grade and I'd have to read the paper to see the extent to which Id agree it rises to the level of cheating.