In the UK the method for dealing with this type of question is detailed in the CAP698. This book includes the graphs plus worked examples.
For the SEP1 the worked example of the calculation of distance to climb uses the wind without any factorisation. But in a similar worked example for the MEP1 the worked solution includes 50% of the stated headwind.
Logically the factorisation should apply to both. But that is no guarantee that the exam questions have not been produced in accordance with the two different methods shown in the CAP698.