Yes, more or less. On the same parallel (equal lattitude) they have the same with. But higher up north/south they have different width. The big 2-letter grids fall out of step with each other. Which makes sense as a degree of longitude becomes smaller as you approach the poles. And so you make up for the area they contain.
I.e. that AG grid (see link below) is a weird one. My point was they fudged the borders (clipped some of the inner grids) a bit to make them fit better to the shores.
http://www.geocities.com/germangrid/enorthenteat.html