Personally I also think 'GH Gut' is at least partly caused from long term lifting of heavy weights and the pushing against the abdominal wall. Where the abs either get stretched or internally weakened from not tightening the muscles during lifting.
You see many guys with weight belts and when they lift they abs expand and press against the belt. Rather than squeezing their abs tight.
I have seen many older bodybuilders who have never used gear or gh have the ole 'gh gut'. So although I think drugs certainly add to it I think its a variety of factors.
Massive bloating is not caused by Growth Hormone, unless used at very high doses. Insulin abuse is the culprit of the massive guts seen today, along with overeating.