Yeah, the McD app is ridiculous. For some items it gives me an add to order dialog and then an add to bag dialog (I might have the order of those two swapped). I'm not sure what the distinction is between adding to the order and adding to the bag.
It also has some ridiculous restrictions. Nearly every week I take advantage of their in-app deal for free medium fries on Friday if you spend at least $1 on other stuff. I make a sandwich at home, order a couple cookies plus the free fries in the app, then go pick them at the McD that is about half a mile from my home.
Occasionally though instead of making a sandwich I decide I'd like to use my McD reward points to get a free burger. But you can't get both a rewards points item and a deal item on the same order.
I end up doing a rewards points order for a free burger, picking that up at the drive through, parking, then doing a cookies plus free fries deal order, and going through the drive through again to get that.
What's the point of not allowing both a rewards item and a deal item on the same order? If the rule was you could only use one reward or deal per day, then it would make some sense.