On December 2010 i wrote an article: automatically move computers to the right OU.
In MDT 2012 update 1 this was an issue: MDT 2012 settings per task sequence
In MDT 2013 this is still a issue:
How to fix:
I changed DeployWiz_SelectTS.vbs file and it work again 
1. Edit DeployWiz_SelectTS.vbs
2. Add after “Dim sTemplate”
Dim sCmd
Set Oshell = createObject(“Wscript.shell”)
3. Add before “End Function” (bottom of page)
sCmd = “wscript.exe “”” & oUtility.ScriptDir & “\ZTIGather.wsf”””
oItem = oSHell.Run(sCmd, , true)
Download DeployWiz_SelectTS2013.7z