A Tekken 6 PKG is not just a zipped copy of the disc. It is a restructured archive designed to fool the PS3 operating system.
Installing the game as a PKG meant the entirety of the data resided on the internal hard drive (which at the time was a SATA II HDD, significantly faster than the Blu-ray drive). tekken 6 pkg
The game's popularity also led to the creation of several spin-offs, including Tekken 6: Bloodline Rebellion, which was released for the PlayStation Portable. The game's success also paved the way for future Tekken games, including Tekken Tag Tournament 2 and Tekken 7. A Tekken 6 PKG is not just a zipped copy of the disc