The following snippet in ox-latex.el processes negative tocdepths
incorrectly:

#+begin_src emacs-lisp
;; Table of contents.
(let ((depth (plist-get info :with-toc)))
  (when depth
    (concat (when (wholenump depth)
              (format "\\setcounter{tocdepth}{%d}\n" depth))
            (plist-get info :latex-toc-command))))
#+end_src

When depth is -1, wholenump form evaluates to nil, and setcounter command is not exported at all.

See, e.g.
https://en.wikibooks.org/wiki/LaTeX/Document_Structure#Sectioning_commands
for example of a negative level use.