There are about as many seasonal or occasional use residential units as there are rent controlled units ~40k. That's out of more than 3.3 million residential units.
Just as articles about rent regulation usually focus on a rent controlled apartment, rather than the far more numerous rent stablized (~1 million) because they make for better stories, so too do empty floor is luxury building on fifth avenue.
But I fail to see much relevance to the larger housing market. Particularly as it relates to the type of working class people this article talks about.