EXACTLY! If a motley is HOMO motley, why should stripe even be called into question?
Maybe because someone who has not made an effort to learn about corn snake genetics comes along. (or is just starting to learn.) They see a visual stripe pattern like the pretties you referred to and my Zen and they know just enough to know that a stripe gene exists and they say "Aha. A striped corn snake."
IMHO:
Motley, maybe with other descriptors added, for genetically homo motley snakes. eg. pinstripe motley.
Stripe, or maybe Genetic Stripe, for snakes that are homo stripe.
Pastiche, (or some other name that lots of people are willing to use), for snakes known to be genetically het motley het stripe.