The same tech works in both directions. Spammer creates 1000 email variants using a LLM, spam filter collapses those 1000 variants back into easily classifiable embeddings
In the end it's content that matters, not the form that it's send to - I don't care if it's my grandma sending me offers for viagra pills, or a spammer, and I don't care about the language either - I just don't want to get such offers.
On the other hand, if there is an e-mail that may be interesting to me, I don't care if it was sent by a human, or by a machine - I want to see it in my inbox.
In other words - it's not about distinguishing human/machine written text. It's about distinguishing content that is worthwhile for me from the one that isn't.