hey dobbin
Im suspecting that the reason for the 9/15 for ishihara is based on the following
The LAPL medical is done via an approved AME doctor, who just like the NPPL medical is declaring that you are fit and healthy and no pathology, ie the doctor is taking responsibility away from CAA/JAA, and therefore a person only meeting the 9/15 will get a night rating through the guidance of the GP.
the CAA/JAA will not recommend the pass of 9/15 and place the 15/15 pass becuase they are not willing to accept a colour deficient pilot to hold a class one medical, even in one scores 13/15 the pass on the test, they still will not allow it.
I suspect that this will be positive and negative, but on the 17 September, people holding a class on medical with VDL limitations will no long hold valid medicals,
hope this might be helpfull