When guys from that era talked Dbol they talked in tabs not mgs, the little Ciba blues Coach talks about were very potent, most guys from that era took lots of them, so much that there was a former study by UCLA back in the day that brought up the concerns of taking high dose orals and its effects on good cholesterol or HDL, basically over 20mgs a day starts dropping it and at 50mgs a day you have 0, they established that in a low HDL environment that premature hardening of the arteries in the south cal bodybuilding community was a huge issue that was ultimately going to result in earlier death than natural death from cardiac issues.
The dosages quoted are to low to give your muscles androgenic or in that era anabolic type hardness to a flat low carb body, basically that hard look could only and can only be stablished in a considerably high androgenic or anabolic environment that has always been the case now and certainly back then. Could Arnold be Arnold on 300mgs Primo and 50mgs DBol with his genetics, possibly these guys countered the water retention from Dbol with basically high protein no carb diets for 6-12 weeks and no carbing up. except for last minute.