Honestly, I lean towards shaming educators who do that. If you can't detect the whiff of LLM with your own senses, then it has been used properly and shouldn't be faulted. If that premise invalidates your assignment, change the assignment. It's not as if you're assigning this work to test the basic mechanics of writing (grammar, sentence/paragraph structure, parallelism, whatever) — I mean, how much of that did you consciously try to teach? My recollection is, not an awful lot; and I can only imagine it's gotten worse since I was in K-12 (and I went to pretty darn good K-12).