EllisLab has been hosting an archive of the CI2 user guide, as it was at the time relevant to ExpressionEngine developers. The expectation was that codeigniter.com (the current site) would come to be considered authoritative by Google, for all things "CodeIgniter".
EllisLab has released EE3, and I would think that their need for the CI2 user guide is diminishing, though they would still have a lot of developers using EE2. They will at some point do a blanket redirect, but it still makes sense for them to keep things the way they are for now. Derek Jones and I correspond occasionally, so I will find out when they are ready to unhook CodeIgniter from their site.
I would suggest that Google is considering us more authoritative every month
According to Alexa, codeigniter.com's "rank" is #9467 worldwide, while ellislab.com is #10093. Lower #s are better.
According to a page rank checked, we have domain/page authority around 75%, while EllisLab is still around 85%.
Take these numbers with a grain of salt - this is just the result of a bit of digging on my part.
James Parry
Project Lead
