Hmm, `man 7 environ` on Linux says “The user's preferred utility to edit text files”, which matches my long-term understanding. The original distinction between `EDITOR` and `VISUAL` was that the latter need not work on a printing terminal. The name `VISUAL` comes from the `ex` command `:visual` — i.e, vi.
export VISUAL=vim
Will make those program use com as the default editor. I believe for works that way for example.