It makes a little more sense in the case of a traditional vehicle with an engine under the hood that would push back against the pedestrian. However, even in the Tesla I'd imagine that if it's lifted it isn't resting on the bumpers the hood sits on and that makes it absorb the energy more. It's really not clear if that functionality is on US bound vehicles. Tesla has said absolutely nothing about this functionality, which I find surprising. The European and Australian orders have started getting new codes in the safety system field of the VIN (6 and 7) but Tesla still hasn't filed an update to the VIN decoding that explains what those mean, which means they aren't sending vehicles with those VIN codes to US bound customers (last update was 12/10/2013).
The Euro NCAP tests put more focus on crash testing for pedestrians than the US ones. So it may be that the US vehicles won't have this functionality at all for a while. Tesla doesn't have a lot of incentive to include it in the US because nobody tests for it. Tesla has so far as I can tell been very strange about not including things they don't have to in jurisdictions they don't. E.G. the security package for EU cars, Immobilizer for Canadian cars. I'd rather they'd deliver the best available technology to everyone.