When you create the MapPoint you have to include the Camera's spatial reference. This worked for me, but it's Pro 3.0:
MapPoint cameraPoint = MapPointBuilderEx.CreateMapPoint(cameraBefore.X,
cameraBefore.Y, cameraBefore.SpatialReference);
var projectedPoint = GeometryEngine.Instance.Project(cameraPoint, SpatialReferences.WGS84) as MapPoint;
MessageBox.Show($@"projected [x,y]: {projectedPoint.X}, {projectedPoint.Y}");