Rel=alternate / canonical implemented for mobile, canonical not being respected

Question

I manage an ecommerce website that has mobile URLs on a subdomain, so m.rootdomain.com.

On the mobile URLs, there's a canonical pointing to the relevant product on the www. subdomain (desktop site).

<link rel="canonical" href="http://www.rootdomain.com/blue-shirt">

On the www subdomain (the desktop site), there's a self-referencing canonical to the product and a rel=alternate link to the mobile product:

<link rel="canonical" href="http://www.rootdomain.com/blue-shirt" />
<link rel="alternate" media="only screen and (max-width: 640px)" href="http://m.rootdomain.com/blue-shirt" />

My question is, why are my mobile URLs being indexed? We're following Google's guidelines on this (found here: https://developers.google.com/webmasters/smartphone-sites/details)

Any insight on this would be great.

Answer 1

Google will continue to index the mobile pages as well as the desktop pages as the Googlebot considers them separate pages even though they contain much the same data. The purpose of this is so that when someone does a search and wants mobile pages only the page exists in the index already and the user doesn't have to be directed through the desktop site only to be redirected to the mobile site and visa versa.