For one thing, I'm not sure any studies have ever been done which look at the drop in DHT levels in people on high doses of AAS. The studies I've seen were all done with men having normal, physiologic levels of testosterone.
For another, even if you drop the DHT levels enough to have a positive effect on the follicle, does that translate into decrease muscle mass? DHT exerts much of its effects in the skin and follicular tissues, test in muscle.
Any other ideas?