Fair warning, I'm not an admin or anyone. Just a random user.
Global site rules: https://endchan.net/.static/globalRules.html
Rule #2 is what you are interested in. That said, the rules were good in general for the time. Easily generated photorealism is a thing these days. Caution is advised as you know certain people will always strive to push past boundaries, or just cause trouble.
My own general impression: Endchan is comfortably open, but not without minimum standards. Rule #3 can also be interpreted as don't do anything that attracts the attention of law enforcement such that it puts the rest of the site and users in danger.
Clearly, cartoon loli was posted on 4chan without problems. Same here.