Buddy, either you are really not understanding it or just doesn't want to understand it. If there is any additional benefits then yes they can list the same pack twice. But if you look at the screenshot (from My Airtel app) below both packs are offering the same benefits and validity. If you want to defend airtel by saying additional benefits will be added post the recharge, I would still say it is a shady practice. They should mention it on the listing itself.
My aunt has a Vi number which I help her with the recharges and in the Vi app it would show the additional benefits which you are talking about. Like, more data or addional days etc. So, it will also list same pack twice but one of the pack will have "just for you" banner and show the additional benefits or discounts etc. Check 2nd screenshot below. That would be the better way of showing things. If Vi has the technology to do this, Airtel surely can.
I believe these things never catch your attention as you are exclusively loyal to airtel for the past 20 years and never used other networks. So you might not know how others operate and just believe whatever airtel does is the right way.