Well, Avis and Budget are part of the same company (Avis Budget Group). They also own Payless and Zipcar as well. AARP has a deal with all of their affiliated companies. It sounds like the magazine editors just didn't get the memo:

https://www.aarp.org/benefits-discou...t-a-car-10043/
https://www.aarp.org/benefits-discou...t-a-car-10133/
https://www.aarp.org/benefits-discou...payless-10103/
https://www.aarp.org/benefits-discou.../zipcar-10117/