So they plugged the same DS flashcards in and they worked on the 3DS. How exactly is that a fail? There certainly wasn’t any hacking involved. All they’re doing is playing DS games in the DS mode.
Keep in mind that all current DSi flashcards, except the CycloDS iEvo, play DSi games using the DS compatibility mode as opposed to the native DSi mode. Because of this, most DSi ROMs are being dumped without the DSi sections. Only a handful of J and F ROMs are actually proper dumps and the developers of the dumper have not, and likely will not, release it to the public.
So in reality, Nintendo has done a surprisingly good job securing the DSi and 3DS and apparently the current generation of DS flashcards is being banned when the next 3DS firmware update is released in the coming weeks.