You may be right. However, I do currently have the two Sedona discount codes saved in my account - presumably those are open to all members and not tied to a specific mileage account. Sedona is a general promotion and not an Insider special, so there is a slight difference, I guess.
It would be really nice to be able to save the Insider codes in My Account since you can only access them from the original e-mail and I don't always save those.