Kv is called the loop gain. It has units of 1/seconds. This is not a gain. If you multiply Kv by a control signal you do not get a velocity.
The open loop gain should have units of velocity per unit of control output.
I see this mistake in many documents because the authors simply copy what has been written before. They have little practical experience.
Notice there is nothing on how to optimize the controller gains. See
my #25 here
http://iyeya.cn/thread-61700-3-1.html
This document shows real applications and knowledge. Notice the example use a controller with proportional gain and velocity and acceleration feed back. This shows some knowledge.
In the pdf the author mentions PID. Why? Only because that is what every body uses but then why use a P-VA for a real system.
The simple answer is that there should be one controller gain for every closed loop pole in the system so there should be a gain that acts on the acceleration.
Digital hydraulic cylinders have only one mechanical proportional gain. Digital hydraulic cylinders can never be optimal.