I do think code review is worthwhile, not sure how you read that from my comment.

A cap on PR size isn't inherently going to make an LLM do a good job of segmenting PRs. It requires careful prompting or manual action, the kind of effort typically exerted by people who already cared enough not to hit such a cap. You may as well just ditch the cap, to save yourself from having to reject a series of PRs rather than just the one.