[maxltv]

It's not forbidden, but it will not work for this purpose as well as a purpose-built enforcement tool. For example, if two students submit the same paper, Grammarly will not flag it, also by design. Faculty still benefits a lot from this because a lot of plagiarism is unintentional or "lazy" - as in students not citing sources, due to ignorance or laziness, rather than students intentionally committing academic dishonesty.