Great question — answering as the UphillTech team:
Sitemaps allow up to 50MB (uncompressed) or 50,000 URLs ( source ). If you are below that, then splitting shouldn't really make any difference to Google. Making them more human readable may have benefits for some LLM crawlers and things that may be looking for additional context, such as "this is a list of pages about X" - however, I do not believe Google will use them in that way. It may also make it easier for you to review if any pages are missing. However, I don't think it will make any difference to SEO.
Full answer by RichardB: https://webmasters.stackexchange.com/a/148797 (CC BY-SA 4.0).
Need it done for your business? UphillTech.