so then there is even one more advantage of the japanese SMS over the oversea one
Indeed. However, the Mark III and the SG-1000 are totally incompatible with Genesis/MD controllers. It's an easy fix though, the reason why they don't work on those systems is because pin 7 is connected to ground, so that messes up the multiplexer chip in the Genesis/MD controller. Just desolder pin 7 or cut the trace for it and you're good to go.
yeah, I figured that out once, but didn't know that the ouversea SMS was built on the same tech level, whilst the JPN SMS already moved on to the MD (and other D-Sub 9 compatible system) standard.