While that may be, the track could still very well be designed with a heartline in mind. Just because track doesn't bank around the heartline doesn't mean that it isn't there. There may be forces being applied to the train via the track and momentum that cause it to take the shape it does (AKA a rollercoaster layout) but that doesn't mean in any way, shape, or form that it's not heartlined. In a case such as the one of Arrow Dynamics coasters, no, there isn't a heartline for parts of the coaster (turns) while there is for other parts (loops usually), however, the parts that aren't are BEYOND easy to see whereas this has raised a debate, leading me to believe that it is completely heatlined. You have to realize that unlike Arrow suspended coasters, B&M cars are not free-swinging and as such, if they want any swinging motion, they have to simulate it themselves. Now, in order to have a smooth transition, especially one between two opposing turns as they were (one clockwise, one counter clockwise)(F@cking right-left for god's sake) a swing is preferable as:
1: it's fun as F@ck
2: it's a smooth way to transition
So why wouldn't they use it? Now to get to the point, when you swing from one side to the other, if you want to make the swing wider, the heartline will be more s-shaped, while the track will maintain a straighter geometry. If you were to rotate exactly around the heartline of an inverted coaster while it traveled straight (no swinging, only rotation), the track would be odd shaped and the transitions wouldn't flow. Remember that forces on an inverted coaster mostly face away from the track rather than towards it like those of a non-inverted coaster.