"emergency braking maneuvers" refers to an additional automated (software) system for automatically applying the brakes in an emergency (that's detected by that additional system).
>2 In Uber’s self-driving system, an emergency brake maneuver refers to a deceleration greater than 6.5 meters per second squared (m/s^2).
So, Uber's self-driving system has command to brake normally, but it cannot "slam" the brakes. The other system from Volvo's is deactivated when Uber's is working and cannot brake at all. Thus, since Volvo's is deactivated and Uber's won't brake if it judges that a deceleration of >6.5 m/s^2 is needed, it turns out that in automated mode, the car actually lacks the ability to trigger emergency braking at all, hoping instead that the driver will somehow notice. But in a sadistic twist, no warning is given to the driver at any moment that they need to slam the brakes.
However, if the safety driver was trained to brake immediately upon warnings it could have worked quite well. But that would negate the removal of e-brake actuation.....
"At 1.3 seconds before impact, the self-driving system determined that an emergency braking maneuver was needed to mitigate a collision (see figure 2). According to Uber, emergency braking maneuvers are not enabled while the vehicle is under computer control, to reduce the potential for erratic vehicle behavior."
I believe you are the one who has misunderstood.