Try this, on the uphill it is ideal that your tires do not skid, NOT EVEN ONCE. Try a RWD car on the hillclimb and see if you can do a run at full speed without doing a burnout in the rear. Throttle control skills are a representation of your driving skills. Novices usually full throttle everywhere and slide all over the place. Amateurs can half-throttle out of corners and keep a steady line, however slow. Then experienced drivers can exit corners at 75% throttle, thus fast. Practice hard enough and a "pro" level would be going full throttle nearly everywhere BUT without sliding the tires at all and keeping grip at all times. That's how the ultra fast times are achieved.
You can try it on the downhill too but throttle control there is a lot more subtle and less apparent, especially when driving modestly underpowered B class cars. Again, practice enough and it will become second nature.