Hmm... My understanding had always been that a charm quilt was made of all one SHAPE piece, in which you didn't ever repeat the fabric... (hexagon, diamond, square, triangle, rectangle)....
I think the manufacturers sell what they call charm squares and 5" just kind of happened....I know nickel quilts would use only 5" squares to start with....
or, I could be wrong...(although THAT'S never happened before... :lol: )