This is the only technical way to actually run a PS3 game on PS4 hardware. Instead of "converting" the game to a PS4 PKG, you are turning your PS4 into a Linux PC and running an emulator.

The process is a niche within a niche. It showcases incredible community engineering, but it can’t rewrite hardware realities. Use it for obscure titles, small experiments, or nostalgia—but keep your PS3 plugged in for serious gaming.

not possible to natively run PS3 PKG files on a PS4 because the two systems use entirely different hardware architectures (Cell for PS3 vs. x86-64 for PS4)