Upon checking the Microsoft Update Catalog on the Internet, i noticed that Service Manager is not listed/published on the Catalog as well, this explains why SCSM updates are not listed in the WSUS. For the current state WSUS is not designed to give SCSM under Products and Classifications as its not yet under the Catalog.
As for the System Center 2012 R2, they were just released less than 2 month ago and the next expected Rollup Will be mostly in the first quarter of 2014. I double checked with Microsoft Support team and they replied back that the Product team is working on WSUS hotfix/Service Pack/Release..........etc that might list the 2012 R2 Products.
Recommended links for WSUS
- Microsoft Update Catalog: http://catalog.update.microsoft.com
- Deploy WSUS 2012 and 2012R2 in your organization: http://technet.microsoft.com/en-us/library/hh852340.aspx