Misha may not simply say the knots in the barbed wire were shiny because they may not actually be shiny, or because there may be other characteristics or details about the knots that are more important or relevant to the story or situation. Misha may also want to convey a certain mood or atmosphere by describing the knots in a different way. Additionally, Misha may be trying to engage the reader's imagination and evoke a specific visual image by using more descriptive language.
