Here’s another example:
Say you have a lazy researcher. They flip a coin, and if it comes up heads, they do the experiment. If it comes up tails, they just write down a random number.
If you _only get access_ to the final number, then you should discount what they wrote down – it’s 50% likely to be fake.
If you do 1,000,000 simulations of this, it’s useless 50% of the time.
But if you know the result of the coin flip, it doesn’t matter whether they would have generated a nonsense number in a different timeline, or that they’re not reliably accurate. _You know_ they’re reliably accurate in _this case_, so you can trust their data.