I don’t think its a dox unless you prepare a dossier. Just learning someone’s PII isn’t doxing them
You are kind of wrong in two ways. First Doxxing is where you reveal someone’s information to the public without there consent. Usually this is done to get members of the public to harass or harm the victim in some way.
The second part of where you are wrong is the use of the term PII. PII is does not include active surveillance. It is things like your birth date, SSN and records.