I just went to the 3ds eshop, both mgs3d and re:re are usk 16 and there is no ristriction on them. I don't think there is anything 18+ on the 3ds eshop yet. at least I couldn't find anything.According to PEGI, Metal Gear Solid 3: Snake Eater 3D and Resident Evil The Mercenaries 3D
In the UK they were rated 15 by the bbfc. IIRC someone did say on the Nintendo videos, there was a video that was for over 18 and couldn't be viewed till after 11pm as well.
btw: something sounds odd about the time... 11pm till 3am doesn't sound right. anyone who can check tonight if this is true? I've been given false information by the support once before. Would be interessting if someone could check at lets say 10:30pm and sometime between 3 and 6. because usually the content is blocked between 10 and 6 o'clock as it has been mentioned in this thread.
edit: Another thing I was thinking about:
the firmware was obviously done by ncl in japan... so what if they didn't consider this problem when they made the software? Would be a huge overlook on their end but could also mean that this can/will be fixed.