RNG is completely irrelevant to frames, it just happens to progress at speeds that equal a frame. You are thinking RNG manipulation through frames like on the 3DS, but fast forward speeds up the entire game. It DOES change RNG and at the same rate the frames change, but that's not what you use fast forward for. Also, just for the record, frameskipping is a thing and doesn't affect RNG because frames and RNG just happen to match, they aren't dependent on one another.