Well, that's a reason for "K9", to be universal version of N8, I guess. N8 was their first signature series model, co-tuned with a help of Nathan East and targeted toward musicians, similar to A18S. So, perhaps that is a reason for custom-only release. Also, keep in mind, when dealing with universal show demo (like they had for A18S at CanJam) your tuning might not be exactly the same as custom because you are playing with different eartips that will control a seal and will affect the low end response.
The funny thing, N8 name really came from N-eight (Nathan -> Nate), even so it's 9 driver hybrid. Thus, K9 would describe it better, even so K9 is not the official name, but rather a place holder, as 64 Audio rep mentioned at CanJam NYC.