No, it isn't always the case. It is only the case when all employees are fully 100% utilized at all stages of the product, which rarely happens. There are oft

No, it isn't always the case. It is only the case when all employees are fully 100% utilized at all stages of the product, which rarely happens. There are often bottlenecks where one group is blocked by deliverables from another group, and in a perfect world one could make the process more efficient by scheduling so that when those developers would be blocked they are working on the other project. Even accounting for the context switches, having the two projects worked on in parallel would be preferable here if the deadlocking blocks are sufficiently long enough. Having said all of that, doing such scheduling well is damn near impossible in the real-world, as far as I've seen.