[bojan]

Barry,
If you were right, then the there would have been two independently movable scales on two separate circles.. and there is only one.
However, the problem is the design:
Hour angle scale should be coupled with tracking motor (to act as sort of sideral clock), while slewing should be done with the separate motor which moves both the scale and axle. This would significantly complicate the design, though..
BTW, sideral time is hour angle of the ascending node of the Earth orbit (or equinox point in Aries).. but this is not the reason for two sets of numbers on RA/H scale, however this may look convenient at the first glance. I believe the inverse numbers on Hour/RA circle are simply because the mount is sold on both hemispheres.

Similar design issue is with polar finder and totally useless scales associated with it- I have seen some spooky methods to calculate the position angle of the Polaris or SCP.. and I never managed to understand it. The much easier way is just to have a look at CdC.. or to do drift adjustment, or just use the build-in reticle.