But if you bred those third generation snakes back to their parent or to a platty daddy you could get a platty daddy.
It sounds as if you're saying that Lessers from a Platty Daddy clutch do not have the hidden gene, when in reality EVERY one of the offspring from a Platty are ALL het for the hidden gene, the normals and the Lessers.
One of the nice things about this is: You can breed your own Lesser to another Lesser and happen to get a Daddy, or you can even breed your own Lesser to a seemingly normal ball and get a Daddy. I believe every Lesser is from the Daddy, and there are a lot of people with Lessers right now and a lot of normal offspring from Lessers, so you can never really know if you have one with the hidden trait or not.