The ultimate "fault" is clearly with the unfortunate victim of this crash (high on drugs, not paying attention, and crossing where specifically prohibited)
BUT,
The point of autonomous systems is to try to mitigate even such extreme circumstances (drugged up pedestrian wanders into the road) and so it's right to look at the failures in the automation.
Unfortunately, the leading edge of the bonnet is a very stiff structure, and despite "showing little damage" can easily result in fatal head injuries (especially for shorter victims) at a surprisingly low speed.
I should point out that the EEVblog braking (not breaking!) analysis uses a figure of 0.77g, which is actually very low for a typical modern car on a dry road surface. The typical figure for fully developed threshold braking would be around 1.1g and can be up to 1.4g for transient events (before the mass transfer due to the deccel results in less optimum normal load distribution).
If the system had effectively "lifted off" at the 6.5 sec mark (typically around 0.05g) and then swapped to full retard at 1.3 secs, remembering it would have had plenty of time to already "pre arm" the brake system (ie applied a gentle pre-application pressure to push the brake pads out to the discs and stiffen the system so that full braking can be developed almost immediately (~75ms)
It's also worth pointing out that Davids analysis is imo, wrong, as he hasn't considered the fact that we have a time to impact measured at a constant speed, and hence in the distance domain, as you decelerate it takes "Longer" to travel a distance, and hence you then have more time to brake (and hence a 2.55 sec stopping "time" is available!
We know there was 1.3 seconds advanced warning and that the car did not slow before hitting the victim, and so the critical distance was 1.3 sec x 43mph (19.2 m/s) = 24.98m prior to the impact point. (we'll call it 25m). if we take a worst cased and delay the application of braking by 100ms (a long time for modern ABS system) we have (25 - ( 0.1 * 19.2)) = 23m left to stop, under fully developed threshold braking. And at 1 g, it takes just 18m (and 1.95 sec to stop completely from 43mph) ie, we stop 7 meters (more than one whole car length) away from the pedestrian!
In fact, with 23m to stop from 43mph, we can brake at your original -7.5m/s level and still juuuust stop before we hit them!
(this phenomena also explains why, when emergency braking a car, you need to stop hard as early as possible, to give you the most amount of time in which to stop. Most human drivers crash into stuff that they could have in fact actually avoided if they had threshold braked immediately, rather than just got gently on the brakes to start with, and then only braked hard when they realised they needed too, but by then it's too late..... Modern braking systems include a "brake assist" system for this very reason, that actually applies additional pedal force immediately on a rapid lift of the throttle and detection of brake pedal movement. Some drivers angrily complain this makes the car feel like it over reacted, however, what they miss is just how angry and annoyed they would be to spend the next few months in hospital (or on a charge of manslaughter) after actually crashing because they didn't brake hard enough.......)