Setting the "Home Page" value in the Safari Preference Manifest does not work. The policy applies successfully, but the home page does not change on the client.
"Contents of New Windows" needs to be set as well.
Along with the value for "Home Page" the "Contents of New Windows" value must be set as per the following:
0 = show home page
1= show empty page
2 = show same page as current window
3 = show bookmarks
The default is 0