Just now realized why righting arm diagram from the CG MSC report looks the way it does:
This is what a typical righting arm looks like. The report calls it a curve for a notional vessel
This is the righting arm CG-MSC generated using a computer model.
I don’t recall seeing a graph like this before but If I understand it correctly theses curves are the residual righting arm which would be the top graph more or less minus the energy created by the turning of the ship.
The MSC ( Marine Safety Center) stability report is #83 in the docket: NTSB Docket - Docket Management System