Because you have not converted the faces, you have copied the 3d models and you have not even tested ingame, but only by CM.
the head model for FIFA 2014 = 173kb
the head model for FIFA 2015 = 242kb
I see 26 head model of 173kb. Hair model are 2014. Don't COPY the head 2014 in 2015 but MORPHING from 2014 to 2015 head. Hair model aren't possible to convert.
Fix the texture and do new hair model, so rework all.