Now that I have a fancy 101% save file I will say that P ranking the game just goes to show how well the levels are designed here. There is almost always a perfect path where if you can manage it you can go at top speed for a long time. The P rank being based on a combo timer rather then a global level timer is also pretty interesting as it allows for there to be more areas of grace vs a global timer. An area enriched in enemies or items means you can fuck up quite a bit and still get a p rank whereas other, more barren areas require more precision. Granted some of the points sparse areas do seem pretty arbitrary. The second lap's also removing your transformation or item in most levels is another interesting way to differentiate the laps.