It’s so bad that my fiancée has some bras that say she’s a B cup and others that says she’s a D cup. In order to go bra shopping, you have to actually try them on to find out if they fit.
If I had to try on underwear to see if they fit, I might not bother with underwear at all!
Also, sometimes different colours of fabric fit differently in the same bra size.
Most women don’t wear bras that fit.
That inconsistency is not exclusive to women’s undergarments… I bought a half-dozen of the same American Apparel hoodie in different colors… very different fits.
Yes! Also in panties. Usually black, for some reason beyond me, is tighter than any other color both for bras and panties.