Alcohol is lighter than water, so an ounce (by weight) of alcohol is about 1.25 ozs. in volume. 3.2% by weight is 4.0% ABV. ABV sounds sooo much better when you are selling BMC, so legally that's how they are labelled.
I think just about everyone uses ABV.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk