Shantel : Hey, if you're not calling me or other larger-breasted women liars, we're cool.

I do agree that some ridiculous percentage of women (cis and trans) are wearing the wrong size because bra sizing is so confusing, and in all likelihood some of those are in sizes that are too large, but I bet some are also in sizes that are too *small.* And the sister sizing thing is tricky and misleading, because of course your "A-cup" would fit half a dozen breasts of the volume that typically fits in, say, a 34A. I have a friend who's a 28DD, and her breasts are clearly much smaller than mine, even on a very slight frame like hers.
That bra does look comfy, it's true. I prefer underwire these days, but there was a time and breast size/shape when stretchy bras like that were my favorite, too.