I believe nobody told management about the cost of Agile: Management gives up control of the scope. It is the developers who decide how much they will do until the next deadline. If management refuses to give this up, then Agile becomes a farce.
In the words of the manifesto, what management does when it rejects the committed scope of a sprint is contract negotation instead of customer collaboration. The contract in Scrum is: Stakeholders (including management) decide stories and their priority (usually indirectly through a product owner) but the team decides how much they commit to for a sprint.