Restore library and music (manage missing tracks)

Hi all. I'm working with RB since a while, but something still not worked for me: Exporting a library including the tracks gives me folder with all tracks (including sub-folders for artist/album) and ZIP file with the meta data. When restoring the library (e.g. new PC because the old one crashed) I get the library into RB. Then restoring the music files seems not to work, because the "missing tracks auto-relocate feaure" won't search inside this generated sub-folders of the backup. Question: Am I missing something or is this process a little bit stupid? Do I need a tool to flatten the directory hiearchy? When RB exports them into a structure, why does it not recognise this structure? Make no sense to me! Thanks