All the legacy airlines use similar forms of fare logic to set prices based on markets and demand. This is not unique to DL. Ultimately, they have nothing to do with best fare guarantees. Again, the suit is written to make you think that it found lower fares for the same dates and flights, which is the heart of BFG, when it actually never did show that or even claimed that they could. Without showing that, all it is showing is that DL varies prices with demand. Trying to say that BFG does not "align" with demand based pricing is about as silly as saying that it does not align with the fact that the sky is blue. But I suppose if the plaintiff could get enough stupid jurors they could convince them of anything.
In all honesty, the abstract is starting to make my brain hurt, and to have an informed opinion on whether they have a case, I would have to have specific examples (on x date I found y fares that are a violation of the BFG in z manner). That's what evidence in a trial is for.