OP- I think this is a very good question, most of the best,really big bodybuilders before the GH era abused the fuck out of orals. Gh15 takes about igf levels hgh makes in the liver, well orals do this as well through you guessed it (the liver)....,, actually orals increase igf levels more so than injectable steroids for the first 3-4 weeks of use, than at that point it stops going backward and igf levels decline, another reason you dont get shit out of orals past a couple week mark. 3-4 weeks for me....
Of course orals
do not do this to the degree HGH does, nowhere close

..., I dont think any bodybuilder who doesnt use hgh and relies on plain old steroids, will ever reach their full potential without orals. I dont think Menzer,vic richards,arnold, all those guys would have been as large as they were, without using lots of orals. disgusted said orals were used alot more back then than today's guys.
I recall reading a study on adult rats that in rats, who had their pituaitary removed Dianabol had little anabolic effect. It's very possible that one reason why dbol works so well in the real world, and doesnt look like a great drug on paper is because of how dramatically it increases growth hormone levels. No mystery when you take a 23 year old guy and put 15iu of HGH in him, his body goes fucking nuts with the shit.