The great thing about high pivot idler bikes is that there is little to no effect on the drivetrain from pedalling. unlike a VPP or a mid pivot bike, there's no lockout or [extremely limited] chain torque on the suspension. This creates an ideal setup because only rider movement has an effect on the bike's vertical motion. If you're a good pedaller, there's no effect. If you suck, the bike will bounce.
I think, and this isn't really based in science, that the pivot itself has something to do with it. Since the pivot is not near the center of your weight (the BB) you're further from the fulcrum, which makes for less suspension action. Ride a concentric pivot bike and you'll see what I mean. Every movement you make goes straight into the suspension on those bikes. On a high pivot bike, the effect of the weight's motion is minimized because it's not on the axis.
I think, and this isn't really based in science, that the pivot itself has something to do with it. Since the pivot is not near the center of your weight (the BB) you're further from the fulcrum, which makes for less suspension action. Ride a concentric pivot bike and you'll see what I mean. Every movement you make goes straight into the suspension on those bikes. On a high pivot bike, the effect of the weight's motion is minimized because it's not on the axis.