Once you deny PII processing many sites don't load GA etc
The way you phrase this is expressly non-compliant with the GDPR, because what you're describing is an opt-out. To be compliant, websites should only load GA etc after you accept PII processing.
Sorry. They do wait and force a choice before loading the external scripts.
That's the only mechanism one can use to really be compliant as GA (and other providers) stick identifiers onto the session as soon as the script has been loaded.
