Here are the regulatory provisions which are included in the questions.
Section 3.1 of the FDA: No person shall advertise any food, drug, cosmetic or device to the general public as a treatment, preventative or cure for any of the diseases, disorders or abnormal physical states referred to in Schedule A.
103.2 of the NHPR: A natural health product is exempt from subsection 3(1) of the Act with respect to its advertisement to the general public as a preventative, but not as a treatment or cure, for any of the diseases, disorders or abnormal physical states referred to in Schedule A to the Act. Section 103.2 of the NHPR is an enabling provision which sets an exception to the relevant section of the overarching Food and Drugs Act. So yes indeed, a natural product can be promoted to the general public as a preventative for a schedule A disease (provided this is consistent with it’s Health Canada approved Terms of Market Authorization).
Note that the PAAB provides advisory opinions on DTC for prescription, schedule D, and ethical drugs. PAAB does not provide advisory opinions for DTC advertising about NHPs.