Exactitude in writing is like a carpenter building a rocking chair. There are so many designs and types of wood. The creativity for building can be infinite. A rocking chair must be precise, however. If one leg is shorter than the others or the curvature of the base is off, the entire structure could fall apart with the weight of someone wanting to relax.
Calvino acknowledges that vagueness is commonly found in writing and that his opinions don’t reflect the entirety of the reading population. However, I’m going to agree with him here. Writing needs a strong foundation, just like the rocking chair. Vagueness can cause confusion and destroy clarity.