@Conorp - LOL I think that has to do with conical URL's for SEO.

@JLeuze - Yeah, that was more in line with what I thought the term meant but I think in this case, it's for third party plugins not necessarily plugins maintained by the core devs.

@Darren Hoyt - I think it would be easy to figure out what those plugins are with the data the WordPress API collects from plugins installed on all of the self hosted WordPress installs.

@Ron - Your comment actually answers Conorps suggestion of what Canonical.php is for. Don't think aliases has anything to do with these plugins.

@Martin - Yeah, sounds good but I don't like the idea of extending the workload of the core developers by having to maintain these types of plugins.

@westi - Well then, that explains it and what I was looking for. Now it makes sense.