Vortex Sound Research

So I updated my Neutron to the latest firmware and used the app to enable OSC KEY SPLIT mode at C3. I confirmed that if I play two notes, one below and one above C3, it behaves the way the manual indicates:

Notes played below the split point will trigger oscillator 1 and notes above will trigger oscillator 2.

But when I play only one note above C3, I can tell both oscillators are still triggered.

Is this expected? Was excited to learn about this feature, but now I'm bummed that does not appear to work as I was hoping. (Was hoping the the split essentially let me play the oscillators separately, even if just playing one note.)