It is not a lack of sophistication to fail to immediately grasp and assume-true one single subtle undermeaning/interpretation of a vague statement.

It is rational prudence. It is the wilful, deliberate, careful act of steeling one's mind to the resolute knowledge that things are uncertain, and of not seeing patterns where there merely might be, of not projecting meanings onto phrases where meanings are in the mind, of applying what is learned and trained and practiced here on LessWrong.

Or, it might also simply indicate the lack of social training towards guessing passwords.