Official comment
That's because you're trying to use the XML, which points to his collection and the files from his drive. Even if you edit the XML file, you probably don't have the waveform / grid / cue data files, just the songs.
The recommended way to import them would be to connect the drive to your computer, and within rekordbox, click the songs under his DEVICE listing and add them to a new playlist (on that same device), and finally, right-click on the playlist and select Import Playlist. That will allow you to bring the songs AND the data over.