Nope, again, that is not what that means. All consumer electronic devices fall under that law (it is a law, not something of Nintendo's), most just choose not to put it on there. It does not mean that everything does not emit a harmful signal. The law simple means that if it is interfering with a neighbor’s electronics then you have to stop.
I would not turn the DS on anytime that you are asked to not have electronic devices on. You do not know if it is searching for another DS or something.
BTW, if you are wondering how I can be so sure, my dad is a radio engineer. I have read all these laws quite thoroughly. However, I am not a lawyer, so don’t take what I say for stone.
Edit: I just talked to my dad. He confirmed what I just said. He said to try taking an AM radio up against a console system and listen to all the junk it creates. I think most of those have the stickers too.