I experienced male breast growth in my teens, by the time I was in grade 11, I could almost fill a C cup.
Once when we being sized for costumes in musical theatre, after taking my measurements everyone realized I had bigger breasts then some of the girls who had also been outfitted for costumes. I was laughed at and made fun of.
No wonder why I dropped out of the production and that semester of school.
Fast forward 20 years(ouch)...undergoing HRT my breast have increased to a nice fitting D cup.
Partly due to my breast development now, it was time to come out at work. Before HRT I could feel small fat tissue under my nipples, after starting HRT my breast became super sensitive, that fat tissue was no longer there, replaced by breast tissue. Sometimes it hurts to touch but if the discomfort means that there is development then so be it.
Having gynecomastia then starting HRT may not promote bigger breast growth but if you have a bigger breasts at the starting point and then see a cup or two growth needless to say you would have bigger boobs.