It sounds to me like their claim is (or should be) that T-Mobile should've had a 4th box, "become an AARP" member, as an alternative. As it stands, T-Mobile seems to be misleading people by suggesting they don't have that option. Though I guess I can see why neither of them would actually want to say this out loud.

Except that's not a senior discount, as anyone can join AARP.

Are you sure? That page says it's ages 50 and over, which seems like a senior discount. Reading here [1] I see So can you join AARP if you’re Under 50? Yes [...] However, you won’t necessarily get all the benefits available for those over 50. For example, some discounts offered by retailers have age restrictions and require you to be above 50 to take advantage."

[1] https://www.retailmenot.com/blog/why-joining-the-aarp-under-...

Weird. I think of AARP as a political lobbying group - a strange requirement for a phone discount for AT&T. I guess they get payola from AARP?

One need not be a senior to join AARP [1], though some benefits require it. It's not that different from other membership schemes in practice, which is a fairly common business model for special interest groups.

[1]: https://join.aarp.org/sem-bc4-accord-age

40ish, AARP member. Saves a substantial amount on hotels, for example, better benefits than my Amex Platinum care in that regard.

29, AARP member for the British Airways discount.