Not too sure - I never read that many books - and it wasnt an issue at all. I think writing more, without AI, is helping me get back to my pre-AI-stink self.
It's quite different than just reading a lot of text from other authors and passively absorbing diction and style. Instead, it means getting detailed reinforcement signals in the context of your own active writing effort.
This can start an ironic reinforcement learning pattern where the writer gets tuned to write in the LLM's "corrected" form. Imagine a traditional professional writer, in a long-term partnership with a particular copy editor who gates their output.