Because the TRA is a completely different clutch than the PDrive. Adjusting the clickers on the TRA only changed the ramp angle, making it steeper (if going to a higher number) and resisting the roller and flyweight from travelling up it thus causing the engine to rev more. The location of flyweight stayed essentially the same. But don't kid yourself the TRA wasn't the most efficient system- if you're running around on clicker 5 all the time a lot is being left on the table as far as clutching is concerned. Think of it as more of a band-aid for the times you find yourself riding at higher elevations than you normally do you have a way to get build RPM that is lost due to the horsepower loss at elevation.
Now the PDrive has the fly weight incorporated into the ramp. Adjusting the angle of the ramp also changes the location of the flyweight thus causing different changes like overshoot (did someone say popped reeds) at lower clicker positions and harder belt clamping at higher positions.
This is why I said to read the entire page from the race manual not just scan to where it says ABOUT 150 RPM increments as there is a lot of good information in there. There are another couple of other pages discussing the effects on RPM of various locations and amounts of flyweight. But for that you'll have to pick up the race manual yourself. The part number is 484 801 524, I think its around $80.
