Necessary? No. Better? Probably. Despite larger context windows, attention and hallucinations aren’t completely a thing of the past within the expanded context windows today. Splitting to individual pages likely helps ensure that you stay well within a normal context window size that seems to avoid most of these issues. Asking an LLM to maintain attention for a single page is much more achievable than an entire book.

Also, PDF size isn’t a relevant measurement of token lengths when it comes to PDFs which can range from a collection of high quality JPEG images to thousand(s) of pages of text