I'd say this differs per person, influenced by their experiences. Even if I wear a certain letter, I wouldn't dream of calling myself full busted. For example, this me wearing a Freya Gem 28E soft half cup underneath a tight T-Shirt:
If I were to go up to someone and say "I'm fullbusted", they'd propably laugh at my face and make mean comments.
Cup size is all relative in volume; A 28D is after all a 34A, and a 28E is a 38A. I'll admit, I'm probably at the end of what someone would consider small when looking at letters, but if you saw me in person I'd highly doubt you'd regard me as a big busted person, even though I wear D+.
I'm may not be a 28AA or a 30C, but I still want to write articles about this size range. I've still experienced feelings of being a flatchested freak who's not womanly enough, who will never be womanly enough because her breasts aren't good enough by society's standards.
Have you ever had the "Would you wear shoes if you have no feet" joke trown at you? Have you cried in a changing room because no item of clothing looks good on you because of your lack of bust?
Bullying, snide comments, hurtful 'jokes', feelings of inadequacy, feeling ugly, feeling like a freak because everyone arounds you seems bigger, feeling like shit because all the boys like girls with big breasts, and so on, and on, and on. My entire teenage years I was an insecure mess because of my, in my eyes, disgusting body. What's the use of hips & ass if you don't have the accompyaning tits to go with it, is what rang through my mind all the time. On top of that the media favours big chests, and only hour glass figures to boot. Hell, when did anyone underneath an F cup with a non-hourglass figure ever win Curvy Kate's Star in a Bra contest?
After experiencing all this, I'm slowly overcoming my insecurity complex regarding my chest. In the end, I'm more interested in showcasing these problems than arguing whether I'm small enough or not.
We all have our problems, and we all should be taken seriously, no matter what bell curve of the size spectrum we're at, 28AAA or 38L.