To clarify, two examples:
Farmer and his wife: Mindread tells you the location of the key.
The key is always there whether you mindread or not.
Someone's password protected magic coffer: Mindreading the owner gives you the password.
The password only appears as a dialog option after the mindread.
In the case of the key, we want to reward people who adventure out into the world or look in every square meter of a house to find the secrets. So you can either get the key by mindreading or you can spend time to look everywhere and get the reward that way.
In the case of the password, since a dialog has a limited set of replies when the password is asked, it would be too easy to get lucky. That's why in those cases it was decided to leave out the password until after the mindread.
