I think there is a difference in *veins* and *lines*. Tango Amigo has veins. So does Reckless in Denim. I think the Irises that have lines where there are no veins are the Lines & Speckles variation. Reckless Abandon is shown in the Database to be a Variegata, so I think the white lines in the falls are a spray.
Whatever it is, I'm crazy about that Iris!!!