Last year Sony has been given the approval of a patent for emulating older titles on new hardware. This patent essentially emulated games alongside initiating a request from your console. A trophy would pop up within the emulated game giving players the same experience they’ve grown accustomed to and earning trophies for classic games.
With the new PlayStation Plus tiers already live on the other side of the world with North America joining in June, seeing Resistance: Retribution makes sense. Sony is including a PlayStation Plus Classic category for those who upgrade their subscription, offering classic games through your console.