Considering the NIH definitions, it is understandable why the UCSF researcher is making the distinction that he is. Also isn't it just now becoming apparent that HPV-OC is likely actually only a throat cancer?

NIH Definition of throat cancer(also called pharyngeal cancer):

Cancer that forms in tissues of the pharynx (the hollow tube inside the neck that starts behind the nose and ends at the top of the windpipe and esophagus).

Throat cancer includes:
Cancer of the nasopharynx (the upper part of the throat behind the nose),

the oropharynx (the middle part of the pharynx), and the hypopharynx (the bottom part of the pharynx).

Cancer of the larynx (voice box) may also be included as a type of throat cancer.
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Definition of oral cancer:
Cancer that forms in tissues of the lip or mouth. This includes:

the front two thirds of the tongue,

the upper and lower gums, the lining inside the cheeks and lips,

the bottom of the mouth under the tongue,

the bony top of the mouth, and

the small area behind the wisdom teeth.