It's definitely not ideal, but I needed to get this in front of CB more quickly than would permit me to address the various complexities of the AJAX method of pre-populating the values of fields. The examples on the codex are simple because they're related to, say, one custom checkbox that someone added with action hooks. If we're walking through a set of nested FM elements, we'll need to handle a lot of general cases on a variety of different form control types (checkboxes, textfields, select menus etc). I fully intend to do this, and have promised it to CB, but it's not a quick job I don't think.