From Hori's Website: 

HORI Kuro buttons have been designed with less spacing between the housing and button for quicker response

Before there was the short throw Hori Hayabusa pushbutton, Hori entered the parts market with their durable, responsive Kuro pushbutton.   These were made primarily during the fight stick market (controllers that have joysticks, not all button), so only 30mm were available

We recently acquired some HORI RAP V controllers that were used primarily for their PCB and controls.  The buttons were used for initial testing for the pcb functionality, but are unused otherwise.  Note that due to the age of these buttons, there are some minor surface scratches on them.  It's not easy to see and again, the buttons were used for testing