This is nothing but a bad strawman from start to finish. Sprints are not made to help organize things, they're a tool to get more predictable deliveries. Their very short nature forces participants to construct tasks that are easier to estimate and therefore complete on time with a higher probability. This certainly adds overhead to an idealised scenario where people take the shortest reasonble route often enough and…
Yes, sprints on paper are what you describe, but in reality, they rarely ensure deliveries or predictability, they even tend to hinder productivity as they narrow the body of work of a whole team. Think about it, after a week, what is usually the distribution of work of your team? For me, it was always very unbalanced, where people where working overtime and others (best case scenario) would be looking for some work…
Scrum even has a ceremony for fixing this: backlog refinement.