I will try to be brave and post a picture, but it is kind of tough for me. I have a feeling its part of both and the problem is that you cant take back what you learn about you from your enviroment. If it would be smart i would take 5cm to both arms, but that is just too big of a risk. My goal is only bring back the proportion i had before teen age.
Did your arms stop growing in some growth spurt or ware you always short armed? If it makes any difference i come also from a long legged and long armed family. Including uncles, aunts, cousins. My mom looks basically like a spider. Dad has a bit short legs, but a normal armspan.
My limbs are weird, in general.
I have a leg length discrepancy that I need to check with x-rays, and I might about it on the forums. It was bigger than I anticipated.
I never paid attention to my arms' growth, so I can't help there... but my mother is also "short-limbed". She's all torso, with short limbs.
To be fair, if I was extremely rich, and I could know exactly how much humeri lengthening affects its ability to develop muscle and function normally, maybe I'd give it a shot. I also feel that, unlike legs, you don't need a lot of lengthening. However, of course, that's more of a daydreaming thing than anything. Legs are by far my priority.