Not true, once I bought 3 Platinums (1 for me, 2 for friends) and they were all fake. If I clicked save it would save forever. I would try saving and if it saves you should be fine!
Compare the number of fake DS games you see on eBay to the GBA ones. There are more GBA fakes than DS fakes. I know what I'm talking about, so please don't try to say I'm lying when I've been dealing with fake games and helping with identification for years.
That being said, Undertaker Sheep, it would really help if you could play the game and maybe take screenshots, or try to save and see if you have the saving problem like pokemoner2500 had. That'd probably be the final ticket to telling if your games are fake or not.