bug#22348: 24.5; Mode hooks doesn't run as expected if the major mode of a new buffer is determined by the default major mode

[Glenn Morris]

Gosh, that's rather a long bug report. :)

If you do:

./src/emacs -Q --eval "(progn (setq-default major-mode 'text-mode)
  (add-hook 'text-mode-hook (lambda () (message \"FOO\") (sit-for 3))))"
  /tmp/foo.bar 

you'll see it works fine. This suggest that the issue is specific to
point-motion (your example used end-of-buffer).

set-auto-mode calls set-buffer-major-mode if nothing else specifies a mode.
set-buffer-major-mode can operate on buffers other than the current one,
and uses save-excursion to preserve buffer. But set-auto-mode calls it
to operate on current-buffer. Thus save-excursion undoes your hook's
point changes. So that's the real issue here.