This gets complicated when you need to start giving your kids some degree of independence. I would also argue this could be implemented in a more accessibility-oriented approach.
Also, not all 13-year-olds are of equal level of maturity/content appropriate material. I find it very annoying that I can’t just set limits like: no drug-referencing but idgaf about my kid hearing swear words.
On other machines: I do not want certain content to ever be displayed on my work machine. I’d like to have the ability to set that. Someone who has specific background may not want to see things like: children in danger. This could even be applied to their Netflix algorithm. The website: does the dog die, does a good job of categorizing these kinds of content.
But, in essence, they want to strip the ability of parents to give their kids the responsibility you describe. No letting your kids use social media, look adult content, or whatever else. It's simply banned.