That's just to restore the internal state when you reload your save file, so that, for instnace, if you save and quit while looking at a set of card rewards, but haven't made your choice yet, when you reload, you will see the same set of rewards (you can't just reload your save to reroll).

This doesn't really have any impact on the gameplay, and isn't related to the correlation problem, it's just a constraint on the class of RNG algorithms in use, they need to be deterministic with recoverable state.