Yeah, but if stalling is implemented, the clutch is too (infinitely) strong; invincible. Right now, if you wind the RB4 up and drop the clutch in 2nd gear, the clutch will just grab solid and make your tach needle bounce off the pin. If you could stall it, i'd rather burn the clutch a little to be honest (this being a sim).
On a similar note, 4wd shouldn't always be faster at starting than 2wd. There's no way a stock clutch can take more torque than four tyres before slipping.