Maybe with my poor understanding of the English language I missed something , but what about the following link ?

http://connect.microsoft.com/SQLServer/feedback/details/381185/doc-central-management-server-does-not-require-windows-auth

It was a Microsoft Connect feedback created by Aaron Bertrand who wrote

Microsoft closed the connect as someone of the SQL Server Team has modified the documentation

"I have removed the content that incorrectly documented the requirements for use of Windows Authentication. The change will be published in Books Online for SQL Server 2008 R2"

Unless there is a novelty with 2012 or 2014

Have a nice day

PS : I have forgotten : happy Christmas for everybody ( I am in the 25th of December now )