NS3 TcpCubic - GetSsThresh Inconsistent with Linux Implementation

I have noticed in the TcpCubic::GetSsThresh (file tcp-cubic.cc line 418) that the ssThresh field is updated based on the segInFlight value which is not consistent with the linux implementation (source_code Line 355). According to the source code the ssThresh is updated using the snd_cwnd value which is equivalent to the segCwnd field. Can I get help with this?