They will be refering to the fact that they are not legally bound to automatically reflect a 0 balance.
Creditors ARE legally bound to acurately reflect the data. So if the last time they reported the account conduct to the CRA you had a particular status ie Default and an amount outstanding then this is what is should reflect. If they are currently reporting your conduct (I would be supprised) then it should reflect the current status ie 0.
This is also a problem when the debt is sold on as at the point of sale and normally the last update to the CRA you would have had a default and an outstanding balance.
Some lenders will do an update if presured but a vast proportion wont and nor are they legally required to do so.
A very detailed view of how Credit Data can and can't be used can be found here.
http://www.experian.co.uk/corporate/com ... index.html