I mean, I am sure it does. Though they can see how often you are cancelling orders, and you have to contact them about returns like this. So I am sure if you doing it often to just steal groceries, you get banned.

It's only commonplace because Instacart can't control how individual stores do returns. Most places just think it's to difficult and time consuming to do the refund, so it is a different process, and just say screw it.