I just figured out how to use org-babel's :post header to post-process a table and add a proper heading.
(info "(org) Results of Evaluation")
https://www.gnu.org/software/emacs/manual/html_node/org/Results-of-Evaluation.html
Example:
>Helper Function
#+name: add-hline
#+begin_src elisp :var table=""
;; Add an hline after the first row.
(append (list (car table) 'hline) (cdr table))
#+end_src
>Without Post-processing
#+begin_src shell :results output table
df | sed 's/Mounted on/Mounted/'
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