You are right to a point. If you only send all 8 tracks at once to your PC then you'll only get a stereo Wav file (or however you record it)
If you sync your 788 up via MIDI with a sequencer such as cubase, you can record each track individually. It takes time though. A 4 min song, times 8 tracks... 32 minutes of recording + all the setting up.
Mind you, if your sequencer can handle more audio tracks than 8, then it could be worth the effort.
You could also use the 788 as a mixer and record 'live' to you PC as well...
Experiment is the answer... and syncing too... makes life easier..
Good luck... Z