For named ones, eg Brussels certainly have `=terminal` as the 2 piers, but `=terminal` is also wrongly used on the connector section. Are there 1, 3, or 4 terminals? Worse there is a 5th https://www.openstreetmap.org/way/367788803 for the military part. Applications can't make use of such ill-defined data reliably. That's why expanding the use of `=terminal` is poorly conceived. 
Maybe you agree `=concourse` can at least be used inside one `building=` . What about others that think it's fine to use `=terminal` on every "part" of the airport? The definition of `=terminal` is best not be diluted and turned to meaningless. 
In CDG where `=terminal` is used for separate satellite concourse `building=` , the "Liaison" section between 2A and 2C also has `=terminal` added. https://www.openstreetmap.org/way/141149076 