I think there's some misinformation in your replies about how this rating can be used.

As a parent, you can add screen time restrictions to your child's phone that prevent them from accessing apps that are above a certain rating. This is a very powerful feature, that's really hard (impossible?) to bypass without social engineering.

It's possible that discord is concerned enough with this so as to block out nsfw servers. Do they have a lot of teenagers on their platform?