is this transit area ever used and available for int-int pax?
I'm not sure what you're asking. The transit area being spoken about is only for int-int pax.
Basically, if your international flight arrives at a contact stand, instead of going down the escalators to immigration, you go straight and there is the international to international transfer facility (separate immigration and security check, and transfer desks). If your flight arrives at a remote stand, instead of going straight to immigration you go up the escalators to the transfer facility.