Someone walking into a problem cold and coding in front of strangers is not going to produce code of the same caliber as they would if they were given time to think it through (normally features go through grooming and planning before it gets to the developer, which gives them time to research or at least think about the best solutions). They also may come from an environment where speed is valued over accuracy. It's possible code reviews can help with this solution (but sometimes the habit is too engrained and it's better to them to move on to an organization that shares those values).