This depends on some customization of mine. Here's a -Q recipe using a
distillation of my init.

Let /tmp/title-redisplay.el have content:

  (defun my-get-buffer-name ()
    "Get the buffer name. "
    (file-name-nondirectory (or (buffer-file-name)
                                (buffer-name)
                                default-directory)))
  (setq-default frame-title-format '(:eval (my-get-buffer-name)))
  (add-hook 'emacs-startup-hook 'delete-other-windows)
  (global-set-key (kbd "<f4>") 'ff-find-other-file)

cd to the src directory of the Emacs source tree and:

  ./emacs -Q --load /tmp/title-redisplay.el character.h character.c

Then f4, and you'll see the frame title doesn't update.