That's also been my experience: If the bedding block is straight and square.
Recently dropped the barreled action of my Remington 700 .204 into a Stocky's bedding-block stock. The rifle was already very accurate in an epoxy-bedded factory stock, but shot noticeably better after simply bolting it into the new stock.
Very interesting as I always figured that if the bedding is stress free and the recoil lug makes good contact that there wouldn't be any difference. Did you check the first stock for stress free bedding? Was there any other change made, such as a pressure point on the barrel?
I haven't run an aluminum bedding block enough to know much about them. Properly bedded rifles have always returned to the same point of impact for me after removing/replacing the barreled action. By properly bedded I mean stress free, regardless if they had pillars or not.
