The hold rooms are tiny... I thought perhaps IAD would use the new T/Z gates for international arrivals (to streamline the FIS process), but clearly a jumbo-load of pax will not fit in the small terminal space by each gate area!

Perhaps these new gates will be used to replace the "H" gates? When the new train system opens, I presume IAD would retire it's moonbuggies... so it would make sense to move the phantom gates to a terminal.