Going back to the topic in question I believe having additional information added to databases (like recording nationality of claimant) means that the huge DB's need to be re-worked.
This goes in the form of a change request with the outsourcing organisation (DWP use ATOS i believe) and they will no doubt take some time and ask for several hundred grand to do the work, test it and implement it, which is why it will take another year!

Having worked in some of these organisations I know how long these things take and how ridiculous the change controls are and lots of people have to rob the taxpayer some more..