ConfigMgr 2012 R2 does support SQL Server 2014, but only if it had been installed with SQL Server 2012, then upgraded to SQL Server 2014.
The interesting part arises, what if you have to perform a restore of ConfigMgr 2012 R2 on another server? If you install ConfigMgr 2012 R2, the recovery wizard will not work with SQL 2014. Then what?
Microsoft has addressed this issue with the following SQL 2014 restore hotfix (KB 3020755). Turns, out this hotfix is not CU dependent, and can be used to install ConfigMgr 2012 R2 natively with SQL Server 2014.