It’s more fragile than that. E.g. suppose a coin is flipped and on tails, you’ll be given a false memory of being asked your credence for heads, and answering “100%”. On heads you’ll simply be asked the question with no memory alterations. Then in both cases you’ll be asked “are you sure?”
If you’re in the situation of remembering having been asked the question but not answering, then you must be in the heads case, and should answer “100%”. But then when you’re asked “are you sure”, you are no longer sure because you now have exactly the same sort of memories that would have had in the tails case. Your memory hasn’t been altered in this case and you have no new information, so why are you now uncertain about something you were previously rationally certain of?
It’s more fragile than that. E.g. suppose a coin is flipped and on tails, you’ll be given a false memory of being asked your credence for heads, and answering “100%”. On heads you’ll simply be asked the question with no memory alterations. Then in both cases you’ll be asked “are you sure?”
If you’re in the situation of remembering having been asked the question but not answering, then you must be in the heads case, and should answer “100%”. But then when you’re asked “are you sure”, you are no longer sure because you now have exactly the same sort of memories that would have had in the tails case. Your memory hasn’t been altered in this case and you have no new information, so why are you now uncertain about something you were previously rationally certain of?