batch export: org-babel-execute:shell undefined?

[Greg Minshall]

hi.  i am doing an export to HTML using "--batch --eval" to invoke
emacs.

i find that my shell source blocks are *not* being executed unless i use
(custom-set-variables), rather than (setq) or (let), to initialize
'org-babel-load-languages.  to wit...

the following code works:
----
                        (progn
                                (custom-set-variables
                                        '(org-babel-load-languages
                                                '((shell . t)))
                                )
                                (let ((org-confirm-babel-evaluate nil))
                                        (org-html-export-to-html))
                                (if noninteractive
                                        (kill-emacs)))
----

but, with (setq), this does *not* work:
----
                        (progn
                                (setq
                                        org-babel-load-languages
                                                '((shell . t))
                                )
                                (let ((org-confirm-babel-evaluate nil))
                                        (org-html-export-to-html))
                                (if noninteractive
                                        (kill-emacs)))
----

i find that in the latter case, in (org-babel-exp-results),
(org-babel-execute:shell) is not defined.

my emacs command line looks like this:
----
emacs
        -L `find ~/.emacs.d/ -name "org-[0-9]*" -type d` -l org
        -L `find ~/.emacs.d/ -name "htmlize*" -type d` -l htmlize
        --batch ./public/index.org --eval "
----
followed by one or the other above code fragments.

does this ring any bells?  or, any obvious stupidity on my part?

cheers, happy 2021, hopefully.

Greg