Yes the 375 Ruger case is cut down a whopping .4" to give us the 338 and 300 RCM's. The 375 Ruger was also a collaborative effort between Hornady and Ruger to come up with a round which out performs the H&H and is chambered in a standard length action. The case is .4" shorter than the H&H.
If you want to quibble over whether or not that makes it a "compact magnum" or not go ahead, arguing about it is pointless.