The reason is consistency. With the Sidekick, the pusher will provide a guaranteed amount of engagement deadband. Low engagement hubs vary in the degrees to engage each time, depending on where the pawls were to the teeth of the ratchet ring the engagement speed could be anywhere from close to zero degrees up to the maximum number of degrees the system offers. This increases the unpredictability of pedal kickback’s effect on suspension. The other advantage is that the degrees of freedom can be easily adjusted with the Sidekick design. 

Descending on a mountain bike at 15mph (~25kph) a rear hub and 29” rim rotates at 170rpm or nearly 3 times per second. A hub with a 18 degree engagement angle (20 engagement points), could potentially engage over 60 times per second! The likelihood of having pedal kickback in this scenario is extremely high and only increases with hubs that engage faster. 

Faster engagement may be a selling point of some hubs, but it definitely does not lead to better suspension performance. A hub with 1 degree engagement (360 engagement points) can potentially engage over 1000 times per second, practically ensuring pedal kickback and severely limiting suspension performance.