Nes cores deleting save files

Hi, I wanted to ask if this is “normal”, because I just lost the entire save file of Final Fantasy III for the NES.

I was playing on the Nestopia core (Retroarch 1.0.0.2) when I wanted to see how the other cores perform with the game, so I save the game (It workerd well up to that point, I played the entire game several times with the same files, both ROM and Savefile), when I change the core to QuickNes, and discover that loading the game on that core DESTROYS the save file and makes a new one, if you go back to Nestopia, it doesn’t matter because the file is actually erased and gone for good.

It happens with every game that I tried on the NES cores.

It’s that how it’s supposed to work?

If it is, why?