That's because they haven't invented it yet.
The test mules are using the SOHC 3.5L "sport hybrid" system destined for the RL. The NSX system will be a more "robust" version of that powertrain, but Ito has challenged the engineers to come up with a lightweight, high-power variant. I say 6 to 9 months before any prototype is ready. It's a big challenge to say the least.