Yes and no. In a practical sense you're right and I said as much in the second paragraph. As for the legal definition of PII:
NIST Special Publication 800-122 defines PII as "any information about an individual maintained by an agency, including (1) any information that can be used to distinguish or trace an individual‘s identity, such as name, social security number, date and place of birth, mother‘s maiden name, or biometric records; and (2) any other information that is linked or linkable to an individual, such as medical, educational, financial, and employment information."
Part 2 is pretty much met given the data that's being sent to doubleclick. But Part 1 isn't being met. This is an AND statement, so for this to be PII, both parts have to be true.