Admittedly, the command is a little different than how I exposed it on the Grasshopper component but I think you can just have a similar boolean/check-box input as an option on the “Save As gbXML” menu for “All Interior Floors” and that would mean that you just add the following to the command:
@piusto, the new version is now publicly available (v1.43.12). It includes the option that @mingbo mentioned above and here is what the exported gbXML looks like.