I know literally no one reads nor cares about PG-13 or other ratings, after all, I've seen kids unders 10 years old playing GTA V or watching Deadpool in the cinema. So it wouldn't surprise me either that pre-teens under 13 are reading in Webtoon.
However, this YouTuber clearly doesn't know that Webtoon, especially originals used to be suited for mature audiences, with warnings too, where nudity, sexually gratifying content, dismemberment, violence and more was there. Obviously, just like YouTube began to regulate its content at the point that your video gets demonetized if you swear on them, Webtoon began to regulate its content not because they noticed kids under 13 were reading their stories, but because of the pressure from Credit Card companies, both Patreon and Pixiv FANBOX are under this issue as well, despite they are mature oriented.
However, Webtoon does put a warning on its content, but it wouldn't request users their age and limit their access based on their birth date. And as well, a lot of kids just go straight ahead mature content regardless of warnings, some even fake their age in order to get an account to access certain platforms (I was one two, literally made a Tapas account and faked my age just to read the NSFW scenes of a comic I liked)

A lot of artists have Patreons without making NSFW, and even those that they do, you'll have to check their tiers to properly see what they are offering in exchange of your support.
Many have:
- Early access of around 3 to more episodes published before public platforms.
- Exclusive illustrations of the characters that doesn't go public (Be it early stages concept art, unused designs, and such)
- IRL process videos with narration of the artist, guiding others onto their creative process
- Tutoring and private classes to either learn how to draw or tell stories.
- Discounts and exclusive merchandise with shipping (plushies, mugs, pins, posters, artbooks, etc)
- High-Res downloadable files or PSDs
- Art requests or commissions
- Resources such as personalized brushes, textures, anything the artist created as a tool for their own series
And other rewards as well. I must remind you that adults... will, likely enjoy or talk about certain adult topics, just because something is NSFW doesn't mean it has to be taboo or involving minors or certain fetishes. And of course, to a certain degree is to interest fellow adults to support them, because, let's be honest, kids don't have the money to support an artist's career. And there is nothing wrong with NSFW, usually the people that do it, also enjoy or has no issue with the content, those that only do it for the money get tired eventually and switch back to being SFW creators.
As well, I don't know why you need to censor words here, there is no algorithm like TikTok or Facebook that'll get your account suspended or shadowbanned.
Not to mention, while this may not happen in the forum since there is no such a function, in other platforms like Tumblr, people filter words to avoid seeing certain content, if you use asterisk or write the word wrongly, it won't be filtered and it'll show to those that were originally trying to evade it.