I very much doubt that the J versions, including JDM only models are always completely made in Japan. Maybe just the movement. I'm not sure what requirements are there to tag the watch as MIJ, but I have tried MIJ vs non-MIJ, they are literally the same with small difference.
http://forums.watchuseek.com/f281/differences-between-skx007k-skx007j-explained-81783.html
Fact is, a lot of the J models available in Singapore are made for the Middle Eastern market, which allows them to be tagged as MIJ because of the laws there (company origin, not watch manufacture origin). So all of the people paying a premium price for J models *and* thinking that there is a difference, better polishing, better QC.. are just smoking some crack pipe and living a dream.
MIJ vs Made in Malaysia for difference of $20-$50? Wait long long..