Rotation is relative to the entity's local coordinates, which is really the intuitive way to do it.
For example, suppose you are an entity. I tell you to walk forward mile, then turn right 90 degrees. You make the turn 'in place' at your new location. You don't move quarter of the way around a one mile radius circle.
For example, suppose you are an entity. I tell you to walk forward mile, then turn right 90 degrees. You make the turn 'in place' at your new location. You don't move quarter of the way around a one mile radius circle.