The new chapter of the saga is suffering from the "Bloodborne syndrome," presenting better frame-rate in the original and not improved version of the Playstation 4. As with Bloodborne, the new "Final Fantasy XV" is also presenting mixed results in terms of game performance.
Some "Final FantasyXV " players have been doing test that the frame-rates of the game show better results on the original Playstation 4 than in its latest version, PS4 Pro, especially with regard to the quality of image definition. As the tests in the different versions of Playstation show, the game presents problems in the rhythm of the frames whenever the image quality changes from normal to high definition. The same as happened with Bloodborne when it was launched and tested.
This means that despite having the same frame-rates, the image and the fluidity of the game will not look fluid when in high definition. Based on the scenario above, some "Final Fantasy XV" players predict that the decreasing resolution and fluidity is because the resolution in PS4 Pro is higher.
In top of that, "Final Fantasy XV" seemed to need a software improvement so players in PS 4 Pro can definitely enjoy good graphics and fluidity even in a high resolution graphic settings. Perhaps, there will be a major update done by the developer to fix this problem.
However, the game is still playable and will not interrupt you unless you are at the moment when graphics on the game need to render higher than usual. This phenomenon happens usually when the players enter the fighting mode or just watching the trailer. As people know, games like "Final Fantasy XV" needs a good graphic machine even for just playing its trailer each episode.