Clipless pedals make it harder to do that put your left foot on and swing over all in one step. Clipless are pretty slippery for that move and then there is the woops got clipped in already and can't maneuver well enough to get the other leg thrown over and clipped in.

I also can do a running fling ala cyclocross, but again, this would be sort of hard with road clipless since they are slippery and might slip out under you on the road before you could get enough lift to get over your saddle.

I only do the cyclocross start with mountain bike type shoes so I don't slip out.