It is hard for me to agree with that, because it splits a hair in a way that is not genuine. For example, when i owned my art gallery, I would go to my represented artists studio to take photos when they are working. Yes it is a portrait. Yes they are working, rather than sitting in stereotypical pose like sitting in a chair holding paint brushes, and touching their chin like they are deep in thought. But these more natural looking photos are not candid, the artist (subject) knows what i am doing, they adjust their movements, expressions even ever so slightly, they are conscious of how they appear. That is not really candid. The moment of consciousness of the camera is the change of candid to portrait, because the subject is active. I will give you that they may loose their self for a moment and forget about the camera. but that slips back into candid, in my opinion
Can it be valued as a portrait to the subject certainly. But photography is about what is happening in the decisive moment of taking a picture. Aware or un aware in this instance.
And bringing it back this niche with it's talk of "pretty subjects", and street "backgrounds", and portraits being candid isn't very accurate to the title Street-style , and I suspect is holding up the more accurate Street Style niche in this topic, that came after the fact, from being purchased.