We don’t often like to think that when we build something, or have a creative idea that randomness comes to light. Often we gloss over it by attributing the insight to ourselves.
Often the only time we may give full credit to randomness is when it works in our favor. Like- wow, I would have never thought of that without having seen this context.
When we initially constructed the front wall fence, it abutted a chain link fence that closed off the back yard. Later the chain link fence was removed posing a design problem on how to make the turn with the new fence. To keep abreast of the side walk we added a 4by6 and made our turn, leaving its corners as a reveal which shared the tonal values of the deeper green made for ground contact PT wood.
But when it’s obviously a blow out, something not planned and the design looks poorly because of it: then one calls it a mistake.
Knowing where you will end up when you start a project, down to the last board is ideal. Try as I might to avoid design flaws, they show up and by virtue of experience they can be reduced.
A tool to avoid unsought for construction flaws is to build models of what you want built. This has helped immensely.