I see these two things listed constantly, and rightly so because they are intertwined.
We all want to pass to some extent or the other. Frankly I am much more comfortable now that I am not really trying to pass for anything more than a Transwoman. I am not trying to fool anyone, but since I put in the effort to look like a lady, I expect to be treated like one.
Anyway most CD's do look like a wrestler when wearing a dress or skirt and top because they put on a big ol' pair of breast forms to match their broad shoulders and ignore their hips and butt short of maybe a waist cincher or corset.
The GM and GG bodies are different in more ways than breasts and genitals. There are major differences in muscle mass, fat distribution, and even the bone structure. Nothing, not even HRT is going to make your shoulders appear as narrow and your hips as curvy as an average GG of your height/weight. Therefor you need to pad your hips and butt (maybe even thighs) to balance your figure.