You’re second point is a good one, but you absolutely can log the IP which requested robots.txt. That’s just a standard part of any http server ever, no JavaScript needed.

This makes perfect sense. Thank you!

That makes some amount of sense. I’m not sure exactly how each article is stitched together to create the full file. Do you happen to know if it’s just put together sequentially or if there’s XORing or more complex algorithm going on there? If it’s only the former, they would still be hosting copyrighted content, just a bit less of it.

EDIT:
https://sabnzbd.org/wiki/extra/nzb-spec
This implies that they are just individually decoded and stitched together.