Happens all the time. DL sold me a 23 min connection in AMS. I happily took it, knowing that they'd have to clean up their mistake (and when they did, I ended up with the exact -sold out- flights I wanted). I've seen shorter connections than that on DL.com, as well as flights that don't exist (e.g., MUC-SLC non-stop). I happy to buy any of these, considering that a mileage refund is the worst that can happen to me.

To the OP: Don't wait too long to inquire about your change. They sold you a flight that violates the MCT requirement. They need to clean it up (and you don't have to pay a dime). Cleaning it up can be difficult if partners are involved and you wait too long (because flights my be full).