Too Detailed, Too Fast
One of the dangers system designers continually face is diving into too much detail, too fast. Given a system problem statement, the tendency is to jump right into fine-grained function (feature) definitions so that the implementation can get staffed and started pronto. Chop-chop, aren’t you done yet?
The danger in bypassing a multi-leveled analysis/synthesis effort and directly mapping the problem elements into concrete, buildable functions is that important, unseen, higher level relationships can be missed – and you may pay the price for your haste with massive downstream rework and integration problems. Of course, if the system you’re building is simple enough or you’re adding on to an existing system, then the skip level approach may work out just fine.