That is true in the legal framework. In practical terms the Janitor however will say "I work at Facebook" (as long as they are proud of the brand) not "i work at sublease janitorial management corp" in a social situation as Facebook is where they are. And going back to the original article: Even such contractors sometimes get corporate swag at such places.

True, they go even further like most large tech companies, security(physical), IT, food chefs/preparers, even alot of recruiters are all permanent contractors.