The site can not request the information by itself, so you would have to actively do this procedure by yourself. And why would you try to send a certificate if you are under 18. And this trick only works once in a lifetime only on website that track you in a way (the certificate is not able to be used to track you, afaik not even across individual usages, so if you use a porn website every day and have to send a new certificate every day it’s not able to track you).
The site can not request the information by itself, so you would have to actively do this procedure by yourself. And why would you try to send a certificate if you are under 18. And this trick only works once in a lifetime only on website that track you in a way (the certificate is not able to be used to track you, afaik not even across individual usages, so if you use a porn website every day and have to send a new certificate every day it’s not able to track you).