Just as an update: I discovered that I was running SCCM2012, NOT 2012 SP1 or even R2...
I've upgraded the existing lab environtment to SP1, and after that to R2, and I just checked, the updates are now visible in SCCM.
For everyone's convience here's a blog to check your build # to check what version of SCCM 2012 you're running: http://sccmguy.com/2013/11/12/configuration-manager-2012-cumulative-updates-and-hotfixes/
BTW: unlike other MS SP's, this SP is a part of the full SCCM 2012 SP1 download. So if you want to upgrade from SCCM 2012 to SP1, or R2, you need to download the full SCCM 2012 SP1 download file, mount/extract the file, and use the installer to upgrade to SP1.