In my opinion, an article prefix is a pseudo-category that mangle article names, such as the QA/ in QA/Updates Testing. While prefixes can sometimes appear natural, such as Releases/Rawhide, they are usually unnecessary and distracting. For the most part, articles that have prefixes would be better served by either being in a category, by having a more descriptive name, or not having a prefix whatsoever.
Negative Consequences
Article prefixes are ambiguous
Article prefixes are usually too terse to indicate their purpose, or too generic to be useful. For example, the QA prefix does not indicate whether articles relate to the QA project, quality assurance in general, or articles that are merely relevant to QA. In reality, the prefix is used for all three of these purposes.
Article prefixes miscategorize content
Since prefixes are ambiguous, editors typically are unable to find a single prefix that wholly fits their article. Content gets spread over many different prefixes, and is not predictable or easily accessible. For example, Fedora Release Criteria discusses the criteria for Fedora releases. Releases discusses releases in a broad sense. ReleaseEngineering/Overview also discusses releases, but from a releng point of view. These articles should be merged or reorganized to complement each other, rather than compete.
Article prefixes are inconvenient
Article prefixes make it difficult for editors to link with existing articles. There is no definitive place for content, so very relevant articles end up in very strange, unpredictable places.