Here's why:
* Mechanics encompasses the rules of grammar, punctuation, capitalization, and spelling.
* Content focuses on the ideas and information presented. While poor spelling might make the content harder to understand, it doesn't directly affect the quality of the ideas themselves.
* Organization refers to the structure and flow of the writing. Spelling errors don't impact this aspect.
* Style deals with the writer's voice and choice of language. Spelling errors can make the writing sound less professional or polished, but they don't fundamentally change the style.
Therefore, spelling errors directly impact the mechanics category of writing assessment.