Just did the mod - and interesting results...
First, I saw that the main menu saw displayed the familiar region 4 (US) on one side of the switch, and region 6 on the other - I guess this is Korea.
So when in US mode, everything booted and played fine as it was supposed to.
Turned off the machine, flicked the region switch and put in a Japanese game... Saturn went to the main menu displaying "game not suitable for this region" message. Ugh, so maybe there IS a region check between Korean and Japanese games.
So I threw in a Korean Saturn game and... it didn't play that either! (and remember, they played fine when my other Saturn was in Japanese mode).
So after this experiment, I can come to a few possible conclusions - from least to most likely, in my opinion.
1. I goofed on the mod somewhere.
2. Region 6 really isn't the Korean region. It's some other random place.
3. Although Sega originally included a different regional setting for the Korean market, this was actually never used, and Korean games were actually released with the region 1 (Japanese) stamp.
#1 isn't likely, because had I goofed, the US side of the switch probably wouldn't have worked perfectly, and it also wouldn't have displayed a different region (region 6) in the main menu for the Korean side of the switch. It most likely wouldn't even have booted normally had I really messed up somewhere on the mod itself.
Maybe #2, but I can't verify unless someone with a Korean Samsung Saturn can verify that their Saturn displays region 6 in the main menu of the screen (or checked the jumper settings). I don't even know if Samsung Saturns display this info on the main menu, considering a Japanese Saturn unit I have do not display it.
Most likely #3 - this would explain the supposed 100% interchangeability of games between Korean and Japanese regions, and why my Korean saturn games boot up on region 1 (Japanese), and NOT region 6.
So in the end, in didn't work as I planned, but I learned something out of it. Hopefully it was of interest to some people out there...