yes, exactly.
Likewise "write a novel in the style of Terry Pratchett"
Likewise "write a novel in the style of Terry Pratchett"
So even if your desired system were implemented to a T, you could hire someone to write a dozen or so examples of Terry writing. Probably just 30 or so pages of highly styled copied text, and then train your bot on this corpus to make “Not Terry” content. Boom. $100 on gig author and then for all practical purposes the Terry style is legally open source. Terry doesn’t even get the $100!
Saying "a-HA! But my automated process can produce something that looks much like what your human would!" does not negate that; it merely makes it hard to tell the difference at a glance—which we already know to be the case.