The MakeOTF heurisitics do not have any rules to set the Mac code page bit. This is a bug, that will be fixed in the next FDK release, due out soemtime around July. The only way to set it is to use the CodePageRange override and use a vlvalueaue which sets this bit. As I recall, but please check against the spec, the Mac Code Page is bit 29, aka decimal 536870912 and hex 0x20000000 (I like PCCalc for this kind of conversion - enter 2^29.)
MS Validator complains about most of the Adobe OpenType fonts for just this reason.We still know of no problem caused by this issue, but plan to eventually fix the fonts anyway.