The Configuration Manager 2007 documentation library specifically states that Fast User Switching is unsupported.

The Configuration Manager 2012 documentation library says: "Fast User Switching, available in Windows XP in workgroup computers, is not supported in System Center 2012 Configuration Manager. Fast User Switching is supported for computers that are running Windows Vista or later versions."

Now, I'm reading that as 2012 supports Fast User switching on Windows Vista or later?

I don't think that support scenario is completely accurate, as I am still finding that required user-targeted packages/programs (NOT applications!) do not run for a user who is not the first logged on user on a system with fast user switching permitted. The execmgr.log shows that it knows the policy is there but does not trigger the install command.

Applications seem to work fine, so I believe the documentation should state that SCCM 2012 supports Fast User switching on Windows Vista or later for Application deployment and not package/program deployment?

You should send this to smsdocs@microsoft.com.