the Scrum abstraction is most applicable in the consultancy/client relationship

Estimates are always wrong, so why do estimates at all? Why not just do Lean instead of Scrum? If you are product company building a product with in-house developers who are direct employees, yes, this is the way to go. You just work on what you have to work on anyways. Don't worry too, too much about how long it takes. It has to get done regardless. The reason to do Scrum is to have a burndown chart. The reason to have a burndown chart is for a consultancy to set expectation with its client that things will go off the rails a little bit and that sacrifices will need to be made. This insulates the consultancy from signoff on a waterfall project that balloons out of control because the upfront estimate of scope was wrong because estimates are always wrong. Scrum solves the "estimates are always wrong" problem by making bad estimates in a different way!