The OS has your birthday, but it only reports minor/major when a web services asks. This is better, because when a minor becomes a major, he can keep his device without having to ask parents to unlock it .
It works like this in Android Family Link.
As a parent and a system administrator myself, I think it is brilliant actually. You need age verification somewhere. Having it in the website is bad, because you force people to send their id around. At the DNS level is verg unreliable. Being able to simply set a flag for non-admin accounts and expect legit websites to respect it, makes the DNS solution much more reliable, and removes the need to send your ID and picture around. If it is a tool for parents, it is good.
It becomes bad if the OS is required to DO the age verification, via some DRM-like service that handles your ID and personal data.
Keep up the good work! But please don't ask me to help.