This is probably a reference to Youtube's reaction of the COPPA lawsuit.
Basically, Youtube will hold you responsible if you upload something to Youtube without properly tagging if the content is rated for children or not.
However, they also said that anything that may be related to children (toys, kids' movies, etc.) should be tagged for children.
If you tag something as rated for children and it's not, Youtube will punish you. However, if you talk about a new Frozen movie or review Lego (toys) and use swears, that's children's content with adult language, and therefore punishable.
The FTC has published rules about this[0] but has in the past stated it intended to go after Youtubers who broke the rules.
These toggles also have an impact on how your videos are monetized and functionality [1].
So, an adult reviewing lego and calling it "fucking amazing" might be right in the middle between "FTC lawsuit" and "account banned by Youtube".
Of course this is all further complicated by the fact that other countries will have different legislation. A video marked as viewable for children by the Youtube rules may get you into legal trouble in another country.
I'm not necessarily against COPPA but the way the lawsuit was settled caused quite a stir on Youtube and threatened the income of quite a few people, which was made worse by the terrible UI Google has built into Youtube (you couldn't mark a set of videos as "for children", you had to go through each one, and every day a video was up was a day the FTC could send lawyers after you). If Google had handled this better by providing the necessary tools and clear information, this wouldn't have been a big issue at all.
[0]: https://www.ftc.gov/news-events/blogs/business-blog/2019/11/...
[1]: https://www.vox.com/culture/2019/12/13/21012611/youtube-copp...