The point is, you can be handed 1) the entire source code of the PRNG, and 2) six outputs from it, and it's impossible to know what the starting state of the PR

The point is, you can be handed 1) the entire source code of the PRNG, and 2) six outputs from it, and it's impossible to know what the starting state of the PRNG was because six outputs could have come from many different starting states. You could brute force every single starting state and find every one that would produce those 6 outputs but it still doesn't let you know the next value.