Grooms parents/ Mother

I was told that when selecting the dresses for the mothers of the bride/groom, there is a process...let me explain... "It is the bride's mother who will first select a dress for her daughters wedding. A gown of complimentary color and similar styling is then chosen by the mother of the groom. She must wear long if the bride's mother wears long or short if she wears short. The color should not match the bridesmaids, nor the brides' mother, but compliment both. " Now- is this true?? Is that really 'proper' etiquette?? And will anyone really notice if we left the dress decisions up to our mothers w/o making them 'match'???