The randomness of sizing is infuriating, of course. It's ridiculous. Then there's the vanity sizing, which, IMO, is plain old bad for our health. Carrying more weight than is healthy for our frames has been so utterly normalized and enabled that people are flattered into thinking that they aren't carrying excess weight while they are.
Not that it matters what size someone is comfortable at or has ended up at but I do feel we owe it to ourselves to be realistic about things. I could claim to be a 10-12 with careful shopping, and therefore slim. Actually I'm about the top of the healthy weight range for my height. I'm an old 18-20. I don't care about the number or letter combo that shows what size I am, but still, I'm not 'slim' whatever my clothing labels choose to claim.
Surely it's logical that the smallest available sizes are tiny to the point that most women don't (and wont ever) fit them, just as it's logical that the largest sizes are so big that most women don't fit them. Whatever we call the sizes most of us are probably going to find that we fall somewhere around the middle of the range rather than at either extreme. Unless we allow ourselves to lie to ourselves about stuff.