Do we need gnus-yes-or-no-p and gnus-y-or-n-p?

[Richard Stallman]

    The behavior of `y-or-n-p' that it doesn't clear the question
    and the answer is not serious of course, but I feel it is not
    cool.

It is intentional.

    Currently, it is commented out in the trunk by Reiner Steib.  He
    also wrote the benefit of leaving the question and the answer in
    the echo area as follows:

    (http://article.gmane.org/gmane.emacs.gnus.general/66061)
    > In contrast to yes-or-no-p it is much easier to type y, n,
    > SPC, DEL, etc accidentally, so it might be useful for the user
    > to see what he has typed.

Yes, that is the reason.