That cannot be right.
In "I have not failed", the 'not' comes after the auxiliary verb, and in "I would not have failed" the 'not' comes before the auxiliary verb.
Therefore, whether what you say is true or not, it can't be the answer to the question the OP is asking, which, from what I understand, is precisely the question of why this happens.
You've been asked by a moderator to put "Not a Teacher" in your post. Also if you are going to answer questions, you should be fairly certain that you know the answer, and you certainly shouldn't make such categorical statements.