Ann: Good Oil Conference Presentation, page-24

That's most likely because the northern part of the project area (including PS and Roc fields) is covered by 3D seismic but Dorado isn't. So they can choose whatever orientation line they want over PS and Roc but when they get to Dorado, they can only go along one of the existing 2D seismic lines. Those lines aren't quite in the right orientation to run right down the axis of the Dorado structure.

You are right that this would affect the apparent dip of the Dorado canyon, and the dip of the reservoir strata, but it doesn't affect the true depths - column height and spill point depth, for example, don't change.