No? I think
Crouching means you can not get knocked down, even by the strongest Wook charge or SBD slap, they still get hit by the slap, but they just don't fall over. So no you can not just aim lower or crouch down to their level to knock them down. As Wook, if someone knows to crouch around you, beat them to a pulp, unless they are a siff, then just cry and run away. As SBD, if someone crouches when you try to slap, learn to aim your arm, and kill them, if it's an ARC, you can probably find a time to slap them, but as SBD when it doubt shoot the crap out of them.