How?

Hmmm, not sure how 'solved' is a question :) but I ran into the same problem today. Robots.txt in Concrete5 is preventing the google bot from loading Javascript and Stylesheets. That way you website will fail the test. Remove any directory from robots.txt that contains Javascript files or Stylesheets used in your websites. The main ones are:

/packages/
/js/
/css
/updates

And probably some more depending on what version of Concrete5 you are using.

That's all!

Bull**** or scam?

Test site to be mobile:https://www.google.com/webmasters/tools/mobile-friendly/...

from the google webdev blog:
http://googlewebmastercentral.blogspot.ch/2015/02/finding-more-mobi...

if you have a responsive theme and the google-mobile-friendly-test fails, replace the "robots.text" with following content: (found on github)

concrete5.6:

User-agent: *
Disallow: /config
Disallow: /controllers
Disallow: /elements
Disallow: /helpers
Disallow: /jobs
Disallow: /languages
Disallow: /libraries
Disallow: /mail
Disallow: /models
Disallow: /page_types
Disallow: /single_pages
Disallow: /tools
Disallow: /index.php/tools
Disallow: /blocks/*.php$
Disallow: /blocks/*.xml$
Disallow: /concrete/*.php$
Disallow: /concrete/*.xml$
Disallow: /packages/*.php$
Disallow: /packages/*.xml$
Disallow: /updates/*.php$
Disallow: /updates/*.xml$


for version 5.7 use:

User-agent: *
Disallow: /application/attributes
Disallow: /application/authentication
Disallow: /application/bootstrap
Disallow: /application/config
Disallow: /application/controllers
Disallow: /application/elements
Disallow: /application/helpers
Disallow: /application/jobs
Disallow: /application/languages
Disallow: /application/mail
Disallow: /application/models
Disallow: /application/page_types
Disallow: /application/single_pages
Disallow: /application/tools
Disallow: /application/views

and tada!
google tells you that you have an awesome mobile friendly site.