In software development, the terms 'pre-alpha', 'alpha', 'beta' and 'release candidate' have been used, with 'beta' being a later development stage than 'alpha'. Here, the 'beta' stage may begin when a product is feature complete, but certain development teams may have different standards of what an 'alpha' or 'beta' product should be like.
As 'prerelease information' and 'unused content' have more objective meanings, it is arguably better to use those terms over 'beta' or 'alpha', as it makes the context of an article or discussion clearer.