The settings can be tweaked for sure but, since vehicles would always use their normal speed when closer than 100 meters from the airplane, if you are inside the cockpit, you won't really noticed it, but you will surely notice the improvement in their arrival time.
That's the only way to effectively counteract badly made large airports with like 3-4 parking spots placed too far away from the terminals, instead of being properly spread in multiple staging areas, like they are in reality.
For sure, it can be tweaked !
Actually, this distance of 100 meters is much too low, especially when you are trying to admire the work of GSX Pro from the outside which I love to do from time to time. In fact, you start to believe you are looking at an amazing ground services vehicles Grand Prix race !!!
Personally, I don't care much on the time needed for these vehicles to come. In fact, the way it is designed actually is just very bad for both the timing and the accelerated speed which result in totally unrealistic vehicle displacement on the tarmac. Most of the time, the reduced timing become unrealistically too short and you always can see this silly speed from outside, or even from the cockpit, if the vehicle path is visible from there !
I propose you add a setup which allow to set this speed acceleration factor from zero (no speed change) to the actual very rapid speed factor. Perfect would be to be able to also set the distance at which the speed return to normal speed.