I've done it before, but it has nothing to do with trying to smooth out the ride.
With "ALT CRZ" displayed on the FMA, the airspeed is allowed to fluctuate quite a bit. This is usually a good thing. But in turbulence, the speed will often go to the low limit, then thrust will surge, until you are up against the barber pole when thrust will decrease dramatically. THAT is actually unsafe. Pulling speed and selecting IAS forces the autothrust to maintain speed much more accurately.