I think epic braking the rules makes their case much stronger. If they say "Apple's rules are unfair" they have a much stronger case if they can show damages caused by Apple's unfairness. My guess this is just another example of them showing the courts that Apple cost them $X in lost revenue because they could no longer make any money on macOS.
The update was live for a couple hours, and I am sure a lot of people purchased the cheaper (against the rules) option. They now have an exact number to tell the courts how much they are loosing to Apple, instead of a hypothetical situation where Apple could argue that customers love apple pay and would use apple pay over 3rd party payment systems.
The update was live for a couple hours, and I am sure a lot of people purchased the cheaper (against the rules) option. They now have an exact number to tell the courts how much they are loosing to Apple, instead of a hypothetical situation where Apple could argue that customers love apple pay and would use apple pay over 3rd party payment systems.