Re: C-M-x on defface doesn't always work

[Richard Stallman]

    I think a good solution here is to reset `saved-face' property to nil
    before evaluating the defface form, and to restore its original value
    afterwards.

Why restore it afterwards?  What result is that meant to have?

    Now in a new frame this face appears as merged with customized non-saved
    background and saved foreground.

I don't think that is correct.

When you evaluate a defcustom with C-M-x, it gets rid of the user's
customizations and installs the default value.  Likewise, evaluating a
defface with C-M-x should install the default value and discard the
user's customizations.

     (defsubst face-user-default-spec (face)
       "Return the user's customized face-spec for FACE, or the default if none.
     If there is neither a user setting nor a default for FACE, return nil."
    -  (or (get face 'saved-face)
    +  (or (get face 'customized-face)
    +      (get face 'saved-face)
           (face-default-spec face)))

What's the motive for that change?