This is LO 6.0.7.3 on Windows 7 Enterprise. All other instances of LO have been shut down (I discovered in Linux that this was vital.)
Here is example non-output:
C:\Users\[snip]>"C:\Program Files\LibreOffice\program\swriter.exe" --cat "Some file.docx"
C:\Users\[snip]>
C:\Users\[snip]>"C:\Program Files\LibreOffice\program\swriter.exe" --version
C:\Users\[snip]>
It's in the --help output, so you'd think it should work.
--cat Dump text content of the following files to console
(implies --headless). Cannot be used with --convert-to.
Thanks