At some point (I think it was between 9.2 and 9.3) something was changed in the library format, which required a complete – and backwards-incompatible – reanalysis of your library.
If you’re exporting an X9.3 library and the other person is on X8, I’d guess that might be why it just appears empty when they open it: the library is quite simply in a format that X8 doesn’t understand.