Exactly
With shorter cranks your feet don’t move as far per rotation (with relation to you and the unicycle) as with longer cranks, making it easier to spin faster for longer. Of course there is a tradeoff, with the shorter cranks you can’t put as much torque to the wheel and loose some element of control.
Check out this thread of more info than you ever wanted to know about wheel size/crank length interactions.
Total Gear Ratio (I still think it should be Total Gain Ratio)