Created attachment 100611 [details]
shows the empty space at the bottom
This is 4.2+ related, as the start center was added then. With 9 entries in the recent document list, i notice that the bottom of the list, there is alot of empty space, include a full empty row.
Yes when scrolling the Thumbnail view, there can appear to be space under the thumbnails but you really are at the bottom of the view. This was by Design/UI decision where the Start Center was sized vertically to hold the left side bar.
Start Center can be resized both vertical and horizontal axis. But that size then becomes default for documents launched from start center.
Start Center can be resized down to just the size needed to hold the menu bar and the left side bar. The Thumbnail view gets set wide enough to hold the welcome message if no thumbnails are present. And, Thumbnail view receives a vertical scroll bar if recent documents thumbnails are present with minimum width for 1 thumbnail.