I wouldn’t refer to the intermediate states as a software design. The “trough” is the transition from an old design to a new design. But it’s not a software design itself, and therefore not a worse design. It’s just the fact that if you can’t go from the old to the new design in one go (a typical situation), then you’ll have an intermediate phase where the code base is in a more inconsistent and/or complex state, and therefore objectively worse if it were to stay in that interim state. But it’s not the software design that gets worse before it gets better, unless you’re doing some design exploration (hopefully not in production).