Yes. That's true. But here in my country it is really difficult to find a Micro SD with a capacity less than 2GB. 
My Prototype didn't work with 1GB Unbranded micro SD card. But in the case of this audio module we have no way to check where the error is. If it is simply in SD card, then you may lose hours for troubleshooting.
But as far as I see, the sd cards that fail on this module cannot be read using SdFat or Arduino SD library. In summary if you can read an SD card using SD library then it should work on this audio module as well.