As long as the tracking of the toggle isn't a thing its a perfect compromise.

This concept does not involve any tracking if implemented as designed. The user agent detects the RTA header and triggers parental controls if enabled. Many sites already voluntarily self label. [1] Careful how far one drills down as these sites are NSFW and some may be malicious.

[1] - https://www.shodan.io/search?query=RTA-5042-1996-1400-1577-R...