The writeup does say he remustered to PTI after a couple of years. I would be surprised if wasn't in the RAF Regt originally, acquiring his para wings there. It then goes on to say that he remustered to PTI, becoming a PJI.
The Army have a special badge for their APJIs, like a normal set of para wings, but with APJI in the centre. You have to have the basic parachutist qualification to go on the APJI course, so only one badge required.