The kickstart script refuses to initialize the partition table of a new drive. It reverts to interactive mode to ask the user whether the partition table should be initialized. The kickstart script ignores the 'zerombr yes' command. Solution: In anaconda/text.py, the NewtFstab object initialization forces the zeroMbr parameter to 0 (around source line 207). It should pass todo.zeroMbr as the parameter. Change the line to: todo.fstab = NewtFstab(todo.setupFilesystems, todo.serial, todo.zeroMbr, 0, todo.intf.waitWindow, todo.intf.messageWindow)
behavior verified ... thanks for the report!
Should be fixed in internal development tree.