bug#37840: Missing in the Emacs manuals:

[Juri Linkov]

>> But pop-to-buffer-same-window still follows rules from
>> display-buffer-alist that can override inhibit-same-window.
>
> OK.  Then customizing 'display-buffer-base-action' and
> 'switch-to-buffer-obey-display-actions' alone is not sufficient for
> overriding the behavior of 'switch-to-buffer'.  The user has to
> customize 'display-buffer-alist' as well.
>
> This means that for Konrad's scenario to work, the minimum requirement
> is
>
> (custom-set-variables
>  '(display-buffer-base-action
>    '((display-buffer-reuse-window display-buffer-pop-up-frame)
>      (reusable-frames . 0)))
>  '(display-buffer-alist
>    '(("\\*.*\\*" . (nil (inhibit-same-window . t)))))
>  '(switch-to-buffer-obey-display-actions t))

This doesn't look good, indeed.

Then maybe switch-to-buffer-obey-display-actions should be replaced
by another variable switch-to-buffer-display-function that could be
customized to possible options #'pop-to-buffer-same-window,
#'pop-to-buffer or any other custom function (and nil by default).