bug#37840: Missing in the Emacs manuals:

[martin rudalics]

>> What _is_ advertised in the manual?
>
> To quote from Section 28.13.5:
>
> Let's consider a user who, as a rule, prefers to display buffers on another 
frame. Such a user might provide the following customization:
>       (customize-set-variable
>        'display-buffer-base-action
>        '((display-buffer-reuse-window display-buffer-pop-up-frame)
>          (reusable-frames . 0)))
> This setting will cause display-buffer to first try to find a window showing 
the buffer on a visible or iconified frame and, if no such frame exists, pop up a 
new frame.
>
>
> The words  “another”  and “new”  suggest a behavior different from what I 
described above.

Right.  But this text talks about 'display-buffer' only.  When you
choose a buffer from the Buffers menu you invoke the function
specified by 'menu-bar-select-buffer-function' and the default for
that is ‘switch-to-buffer’ which does not, by default, invoke
'display-buffer'.  So the text you quote does not apply in this case.
It will apply though if you set 'menu-bar-select-buffer-function' to
'pop-to-buffer' or set 'switch-to-buffer-obey-display-actions' to a
non-nil value.

martin