It's not that much of a surprise, really. Measurements are only a starting point. Breasts have wildly varying shapes with wildly different support requirements

It's not that much of a surprise, really. Measurements are only a starting point. Breasts have wildly varying shapes with wildly different support requirements - not to mention plain ol' personal preference. Every brand will have their own specific construction style and fit, with variations between different product lines and sometimes even individual products. You can't fit a pumpkin into a coke bottle, even if they have the same volume. Breasts aren't any different, so you need the right bra size and shape.