How to enforce sub-scripts with {} only for HTML export?

[edgar@openmail.cc]

Hi. I hope that this is not a known issue and that you can help me.

* Short description

If I export this as html

#+begin_src org
    test_my_subs
#+end_src

the corresponding line is exported as

#+begin_src html
    <p>
    test<sub>my</sub><sub>subs</sub>
    </p>
#+end_src

* Expected output

I was expecting the output to be
#+begin_src html
    <p>
    test_my_subs
    </p>
#+end_src

In the [[help:org-export-with-sub-superscripts][documentation]], it 
reads:
#+begin_quote
     Still, ambiguity is possible.  So when in doubt, use {} to enclose
     the sub/superscript.  If you set this variable to the symbol ‘{}’,
     the braces are *required* in order to trigger interpretations as
     sub/superscript.  This can be helpful in documents that need "_"
     frequently in plain text.
#+end_src

What am I doing wrong? Thanks!

* Emacs and Org configuration

I am using this with ~emacs -q~:

#+begin_src emacs-lisp
     (setq
        ;; Use {} for super and subscripts
        org-export-with-sub-superscripts "{}")
#+end_src

#+begin_src emacs-lisp
   (emacs-version)
#+end_src

#+RESULTS:
: GNU Emacs 27.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.27, 
cairo version 1.17.4)
:  of 2021-03-26

#+begin_src emacs-lisp
   (org-version)
#+end_src

#+RESULTS:
: 9.4.6

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