I think the closing note for closed homework questions should explicitly contain a short notice about not being limited to literal homework, perhaps mentioning other cases. Assuming the system allows it, it would be a little improvement of the site at very low cost.
Yes, it is explained in the provided link in the note, how to post such questions properly. But in my experience, many new posters have not got there yet when starting arguing their question is not homework. (Some of them even seem not reading the warning comment till the end, clarifying it. )
It does not help with the user confusion, when the guide link hint how-do-i-ask-homework-questions-on-chemistry-stack-exchange looks like it is really all just about homework.
If it was in a short notice directly in the closure note, it may save all parties from unnecessary clarifications. Some of these arguments are prevented, if senior community members have posted closure warning comments, so it is already clear for OPs. But it is an extra work and is often prevented in cases of direct closures by mods.
The illustrative phrase to be eventually used in the note can be the one in bold from the meta page how-do-i-ask-homework-questions-on-chemistry-stack-exchange:
"This includes not just questions from actual homework assignments, but also self-study problems, puzzles, etc."