The values in the pressure tables are not the line pressure in psi. They are just values from 0-96 which represent the minimum to maximum possible line pressure. All of the various applicable "psi" values are all added together and then used to lookup the force motor current in the force motor table. A look at the code would be required to confirm, but in theory the modifiers should all just add to the main pressure table value and a higher final answer would command more line pressure.
The tables are likely used to create a smoother shift. The performance applications typically seem to only have non-zero values in the 3-2 table. This could partly explained because of 2nd gear using the 2-4 band. The pressure might be dropped so the band doesn't bite too hard and make the shift abrupt. Bands can be trickier to apply because once they start to grab enough mechanical action takes over and makes them apply harder and harder.
But, it could also just be because low speeds in the gear mean low rpm's so when you kick it down the converter is flashing and putting the maximum torque into the transmission hence upping the line pressure. Then, at high speeds the converter is closer to locked so no torque multiplication and you want a softer shift.