Well it's not so much about deliberately / affectedly being original and weird (which is annoying), but just leaving some space for natural idiosyncratic ways of writing.

That's my mental model. First we had calculators. Then spellcheck. Now we have automated "let me google that for you"

Is this an apt analogy? Don't LLMs train off these bland humans you mention? Wouldn't LLMs then also be bland?

Yes, but sometimes that's what's called for. I think I may have found my answer to where LLMs might be useful for short communications: softening something that might be interpreted as "curt" or even "rude" while not really changing the message.

This throws out the possibility of high quality content.