Unfortunately, "Org-mode" (or Orgmode) means two different things: (1) the lightweight markup syntax and (2) the Elisp implementation of a PIM/PKM tool within GNU Emacs.
This seems to be subtle but it results in many misunderstandings and unnecessary discussion issues.
Although I'm using Orgdown and Org-mode for over a decade, I do think that even with an objective point of view, Orgdown does have its benefits from a syntax definition point of view in comparison to Markdown and other lightweight markup languages (LML): https://karl-voit.at/2017/09/23/orgmode-as-markup-only/
Oh and btw, the linked cheat-sheet covers only the most basic Orgdown syntax elements. Within the Orgdown concept, I defined misc "levels" of syntax elements, starting with OD1: https://gitlab.com/publicvoit/orgdown/-/blob/master/doc/Orgd... This also serves as some sort of cheat sheet I guess.