Yes, but it is difficult to state that it would have been "likely" fatal, and even sevral fractures are IMHO a big improvement over death, the whole point is not about the "average" braking time (BTW that same study gives 1.64 seconds average for "steering away" which is probably what most human drivers would have done in a similar situation, instead of braking or instead of only braking), it is the peaks that count.
I mean, it is about the (rightful) expectation that an automated system is safer (faster, more reactive) than the best you can find (not the average, the best) "in nature" among a random set of drivers, just like the state codes (correctly) take the worse case in the sample or however incereases the recommendation to three seconds.
If you play the game suggested on the same site you gave a link to and deliberately count up to three before clicking, you get:
Reaction time: 2916.00ms
Reaction speed age: 89 years old
Playing fairly, you are likely to get values in the range 300-500 ms.
Here is another paper:
https://www.researchgate.net/publication/233039156_Brake_Rea...
that puts it back to around 1-1.5 seconds or however maximum at 1.8 seconds in the very worst cases.
You also mis-cite your numbers. Reaction time to braking in that study was 2.2 seconds, but steering is 1.6 seconds, and beginning to slow is 1.0-1.3 s. Those numbers are also from a study environment; it's plausible to me that people would be more relaxed in a test than if they see a live human appear in front them.
It's likely that the accident still would have been fatal, or at least the pedestrian would have been seriously injured if the safety driver was driving. Based on the video there was only a second or two to react from the time the pedestrian stepped out of the shadows, and human reaction time varies from 0.7 to 3 seconds [1]. One study found the average driver's reaction time is 2.3 seconds.
[1] http://copradar.com/redlight/factors/index.html