After 4 years of using Agile this team (at least the management side of it) has no clue to how Agile works. Its NOT an excuse to ship things faster (even if that is an occasional side benefit)! Its a method to ship things with less bugs and less "missing" features. Its a way of testing early and often so that you don't end up a month away from your deadline with no chance of meeting it. If you get a new use case two days away from the end of a sprint, schedule it for the next sprint. Thank the person who found a hole in your use cases, that is the point of Agile. If you only start finding them at the end of a waterfall cycle there is no way to recover.