True Ameraucanas that are white are the recessive kind of white. When you have this, white to white will always produce white, although sometimes you get an occasional dark feather or two. Your friend may have mixed in some dominant white from who knows where. Two white birds that each carry only one copy of dominant white will throw about 25% dark birds. Dominant white also does not cover up red feathers, so it is used in making the red pyle color. When you don't know the genetic background of the birds you are working with you can often get unexpected results.