while browsing the updates page on Technet I found:
The packaging of cumulative updates changed as of August 31, 2011. The following packages are provided for cumulative updates:
• SharePoint Foundation 2010
• SharePoint Foundation 2010 + SharePoint Server 2010
• SharePoint Foundation 2010 + SharePoint Server 2010 + Project Server 2010
As a result of the new packaging, it is no longer necessary to install the SharePoint Foundation cumulative update and then install the SharePoint Server cumulative update.
Source: http://technet.microsoft.com/en-us/sharepoint/ff800847
