I'm the author, and this is a fair point, but whatever version of Agile you are describing is unrecognizable to me. It is not how most managers seem treat it due to a mixture of poor understanding and organizational pressure (for example: people love getting the brownie points for agreeing to work, and they don't want to take the political hit of ever admitting that some tasks will never be done to a stakeholder).

Most organizations I've seen simply put everything that they've decided needs to happen in the backlog, then do some sprints and call it a day. To be clear, this is not an Agile problem, it's a "our stakeholders have bad incentives and we can't engineer worth a damn" problem, but it is extremely tiresome to hear "not being Agile" being brought up so often instead of dealing with the real issues. To be clear, I am talking about the typical person in management, not your note.