Nice one. In the scenario mentioned, I see the design to sizing to velocity to plan all discussed and concluded. They seldom happen together and give output too. Story map could be stretch for the scenario but breaking down work in meaningful user stories like Daria attempted is a right way. Having an estimate and a velocity gives a sense of what it takes to achieve it. That also gives an opportunity to get feedbacks as development progresses. Often times there is a desire to conclude and the process is one way. i.e. from Business teams to dev teams with a limited understanding of how things may span out during execution. A detailed discussion is not needed but just a structured approach to breaking down work and laying it in a fashion team can deliver is good enough. I have often found breaking down stories with narrative (As a … I want to … So that) immensely helpful in channelizing energy to most important problem ensuring objectives of task what dev team picks up are aligned with expected business outcomes.