This depends on what you mean by “design”. Sketchup is a drafting package and assumes it is the user who is the designer. Sure, there are extensions that make some things easier to draw and so might look like they are designing but those I know about are still really just illustrating.
Whilst I have never designed a log cabin myself, I doubt many are built the way shown in your image. How do the logs fix to the posts, for example?
Sketchup is mainly aimed at people who know how to design but help them to communicate their designs.