I suppose micro light is the license and NPPL an added privilege.
Historically, there was a PPL (Microlight) a licence with no additional ratings, and a PPL (SLMG) also with no additional ratings. Then came the NPPL, a licence, to which the various aircraft ratings (Microlight; SLMG) were appended.
Sadly, the CAA is now so devoid of technical skills relating to training for licences that they have no conception of what the Examiner is up against.