I agree that manufacturers make clothes differently, but label them the same size. It seem to go with the age they are aimed at. A young woman's size 12 body is a different size 12 from a post menopause woman's.
It is very dis heartening to try a shirt or jumper on in your usual size to find it is not long enough.
It annoys me when a dress seems to fit, but has a side zip that does up until you get to the last inch. Then, I suspect because ribs have widened with childbirth or boobs are slightly lower, the rest of the zip won't fasten!
Still, I do seem to find things to buy! x