If I am correct, the clutch without shift is called a clutch kick. I'm pretty sure it's used to keep the wheels spinning during a drift. Used it many times in LFS, and it does help!
Like, when you go into profile settings, and there's a drop down menu saying "racer type" there are four options, race, drift, drag, and cruise. I think rally would fit in there, because it's really a mix of all of those.