In addition to the toe/heel sensors, I'll bet there's an ankle angle sensor. I expect these sensors provide feedback to the controller so the controller 'knows' where the leg/ankle/foot are. The ankle sensor would have to be adjusted for each heel height. The toe/heel sensors may need adjustment. But for $35k, I would expect the controller to adapt to changing conditions. I'd expect accelerometers that track body, knee, leg, foot motions as well as angular sensors that track the parts' relation with each other.
If your leg gets banged around, you *might* find chrome-moly a better material than aluminum. As I understand, C-M's kind-of 'soft', but hardens/toughens very quickly when deformed. Its properties, whatever they be, are why they use it in roll cages, which rarely fail in 200MPH crashes. I could see your Sunday go-to-meetin' leg being aluminum and your trail leg being C-M.