Yes, the content of the edit boxes does come from the exported html.
For each portion of the Org-mode document (as delimited by
org-elements), both the raw Org-mode text and the HTML are exported
side-by-side, then the raw Org-mode text is hidden and the HTML is
displayed, until the [edit] button is pushed at which point JavaScript
is used to hide the HTML and to expose the raw Org-mode text in an edit
box. When edits are committed they are committed one portion (edit-box)
at a time.
Does this make sense?
Why would something need to change for "this" to be reliable?