Your device requires being opened with a hardware configuration of all 8 channels.

When you use plughw:XXXX, ALSA will cycle through many possible configurations to find one that works, then perform "magic" to make it appear to the application that it is configured as was asked for (in your case, because of the audio file, stereo 16 bit @ 48kHz)

When you use hw:XXX, ALSA does nothing on your behalf: the requested configuration must be available at the hardware level.

JACK should have no difficulty using this device, because it doesn't care about the channel count.