ESA for student - appeal

My client is 19 and studying full time, he is in receipt of DLA LRMob & MRCare and has been for many years. He completed his own ESA application during the summer holidays last year as he thought he could claim whilst he wasn’t on his course. He ended the claim when he went back to the course in September. He was found to have no limited capability at WCA and he appealed. He has only come to see us now he has received the enquiry form from the Tribunal Service. However, surely he is exempt the WCA and should be in receipt of ESA. Shouldn’t the DWP have informed his of this or am I missing something. Thanks