i imagine the mach 10 speed is to deliver them quickly to the target while in orbit then afterward to rod will slow to almost terminal velocity before striking.
or not...
:)
A low earth orbiting platform as moving at about 27000 miles per hour. Mach number takes on strange meaning or no meaning when there is little or no atmosphere (need air for sound, therefore speed of sound reference). But if you deorbit into the atmosphere, that 27000 mph very rapidly gets slowed to 100 to 300 mph (maybe 450) depending on shape and mass, before it hits the ground. That’s just frictional drag.