Claiming IS while appealing PCA

Client only on IB has failed his PCA and lodged an appeal which has been accepted as valid. He requested that he be paid ‘appeal rate’ IS while waiting for the hearing and has now been told that he has to actually make a new claim for IS to do this because he is switching from a non-means tested benefit to a means tested benefit.
I suppose there is a certain logic here but I’ve not come across this before - is it correct?

In my experience it is correct - a new claim will be required for IS.