The PAF's Block 52 Vipers still use Pratt & Whitney motors even though everyone else (except Israel I think) switched to GE. It's much easier and cheaper to maintain a powerplant from a manufacturer you're already using, rather than switching manufacturers late in the game. If a switch was made, all older blocks would be switched during overhaul, but for a long time it would mean maintaining 2 separate engine pipelines, which would raise the program cost. That's something the PAF would avoid if possible.
"The aircraft is installed with many commercial off-the-shelf technologies from the state-owned Aviation Industry Corporation of China, the report said. These include a new and larger holographic wide-angle head-up display and integrated cockpit display similar to the one used by the J-20"
Interesting that technologies used in JF-17 (or J-20 for that matter) are classified as being "commercial off-the-shelf".