I'm hoping the 19H1 skip ahead already has a fix for the issue. I just haven't had the time to go back to the alpha builds on my XB1X. Maybe someone else has it and can let us know
Display – Dolby Vision & HDR - Fixes to the performance of Dolby Vision for the Netflix App. - Fixes to ensure that HDR content is shown as HDR content and not SDR (Standard) content as some users were seeing in the Movies and TV app and the Netflix App.