Parental controls means the control is done by the parents.. not by the companies. I don't need to tell any company what age bracket my kid might be, all I need is for them to tell me how can I block / restrict access to their services in my parent-controlled network (or how to allow them, if using allowlist).

Standardization of parental controls would be if routers and/or the OS of the devices came with standardized proxy settings that allowed privoxy-style blocking of sites in a customizable way so we can decide which services to allow... with perhaps blocklists / allowlists circulating in a similar way as adblockers do.

If a web service wants to offer a highly restricted and actively moderated kid-friendly version of their service, they are the ones who need to provide facilities to us so WE can make the filtering (say.. they can use a separate subdomain.. or make use of special http headers that signal for kid-friendliness), not ask personal information from us just so THEY can take the decision on our behalf...