export XLIFF 1.2 doesn't include topics under submaps

FM 17, Windows 11.

Resuming our documentation development, I need to maintain the documents in two languages.

I originally hoped to compose the original documents in English, then XLIFF everything to the other language, resulting in two complete sets of XMLs.

1. Unfortunately, exporting the book ditamap only includes the single topics and submaps are skipped. Does FM expect us to manually exporting every submaps in the book ditamap?

2. Exporting the FM book is a bad idea, since I would keep working on the ditamaps for layout and relocating topics long after translation has been done. 

Regards,

Andy