Thread:Manual talk:Short URL/Apache/Redirect long urls/reply (3)

That's the intended behaviour of short URLs. If the /index.php url is perfect then no redirection is performed. Wikipedia doesn't redirect /w/index.php either.

See https://en.wikipedia.org/w/index.php?title=Penguin

The only time that redirection is performed is when the title param/article path text doesn't match the normalized form of the title and there is no additional query.

For example see https://en.wikipedia.org/wiki/penguin and https://en.wikipedia.org/w/index.php?title=penguin

The normalized form of "penguin" is "Penguin" so when the case doesn't match the proper one MW does a redirect. Coincidentally sending you from /index.php to /wiki because the redirection itself is done using the Title's url returning methods.

The exception to this as I mentioned is when there are extra query arguments. See how https://en.wikipedia.org/w/index.php?title=penguin&action=edit doesn't redirect even though it doesn't when the action=edit is missing.