I don't doubt @Per Jacobsen's answer. Nevertheless, you should try creating a sample list with some taxonomyfield values filled out.
Then, choose to save that list out as a list template (.stp file). Be sure to check the box to preserve existing data.
Download the .stp file to your PC, change the extension to .cab.
Use a program like IZarc to open and explore the contents of the .cab file.
Within that, you should be able to find a data/xml file that shows how SharePoint prefers to save out the ROW data. Maybe it skips it, but, maybe the mystery is solved within.
I've used this technique in the past to port the ROW data over into my Visual Studio list-instance features, where I wanted the feature to create a list pre-filled with data.