Read The FCP Manual. Volume One. Chapter 17 “Exporting Edit Decision Lists (EDLs) and Batch Lists”
Here’s What Gives…
“A superimposed video track, or any track other than V1, is called a key track in an EDL. Only
one key track can be in an EDL, so information for V1 and V2 tracks only appears in an
exported EDL. ”
Meaning you have to export separate EDLs for each added track.
The EDL format was set up in the 1970’s as a means of saving, well, Edit Decisions, on linear edit controlers.
The ability to stack more than a background and a key track was not anticipated nor built into it, that was pretty much all you needed.