Aunt Petunia shrieked and fell backward over the coffee table; Uncle Vernon caught her before she hit the floor, and gaped, speechless, at the Weasleys, all of whom had bright red hair, including Fred and George, who were identical to the last freckle.
As I understand, "A is identical to B" means A and B are the same. But in this context, the phrase seems to be used in a different way. It sounds like it conveys both Fred and George were exactly identical (from the first) to the last freckle. Is my understanding correct?