As noted many times before, that rate method has long been standard for ETSI patents, has some good reasons behind it, and was even approved by the US DOJ back in 2002:
So no, that was hardly "egregious". It's quite common. For example, Qualcomm's market value is greatly based upon what their current per-device percentage rates are.
Many things that might not make sense to the layman, have been policy for decades.
That's why it's not been fair to either side, that rule changes are being applied in the middle of cases.
The good thing that's coming out of all this, is that various agencies might just finally get their act together, and come up with a modern, cohesive set of rules that everyone will know ahead of time, and be applied across the board.
Net sales. Not gross sales. Of the licensed product. The licensed product, in this case, is not the phone but the chip.