According to the video, the on-board PCM must be much more than the 400 MB somebody mentioned in another thread. So probably it was somehow mixed up with the 400 MB of user storage.
I assume they have raised the PCM waveROM to the Krome level just by implementing its German Grand piano and e-pianos, but let's see...
Although I'm not impressed by the video yet, I think it's appalling how some Youtube users are already starting a shitstorm about it without the details being clear.