Player agency isn't being used as a term to demean any playstyle or to promote a particular game type or anything like that. It's being used to promote clarity and accuracy regarding whose agency is actually involved when playing a game: i.e., the player. It's an attempt to de-jargon the discussion.
Eh. It is my observation (for whatever that is worth) that the term is generally being put forward by people who are particularly interested in games that are asserted to focus on, or enhance, player agency, and is often brought forth to criticize games that have agency elsewhere. So, there does seem to be an agenda back there.