Exactly.

Airlines might oversell economy, for example, by a bunch of seats because they want to maximize revenue - so they will sell more economy seats than they have if premium economy or business are empty because they know they can seat those extra people from economy in other seats on the plane

AirFrance does this by moving people with status up 1 cabin - again only if overbooked. So they bump their Platinums etc up to make space for the no status people with economy reservationa but without a seat assignment