"Smart" size maybe cheaper for the manufacturer, not having to make accurate sizing (which would mean MORE sizes with two measurements each), but it is definitely NOT smart for Customer.

Bras have 2 measurements for a reason.  I wear a 48B bra. I bought an X-Large. Large or X-Large are fine for the CUPS, but the BAND of an X-Large is definitely NOT fine - it is much too tight.  If there was a 2x or 3x, then the BAND might be fine, but the CUPS would be too large.

If this bra had TWO size measurements, 1 for the band AND 1 for the cup, as it should, then I could buy one to fit and I think it would be my go-to bra then - I would buy many of them.

Come to think of it, so-called "smart" sizing might not be all that smart for the manufacturer either - they are losing a lot of sales from all of the people whom these bras won't fit properly.

I GUARANTEE this "smart sizing" idea was thought up by a MAN, who has NO CLUE about anything but producing cheaper bras that have no left-over sizes to be marked down.  A woman would never be so stupid as to think ALL skinny people have tiny breasts and ALL larger people have ginormous breasts.