I'm guessing the innovation here is that this is a single 300Gbps channel. You can fit >50 of these channels on a single fiber. The 10,000km is more impressive if unregenerated.
Yea, that's what they meant later here:
> Ultimately, the company expects 8QAM to let submarine cables carry 15 Tbps per fibre pair.
The big question is how good was latency/jitter over that cable.