IIRC someone had said that there are physical limitations to what one can actually do (namely, having to physically unplug the connector for one safety system in order to be able to add your own at all)
Sure, if you want to move fast and disrupt yada yada. They shouldn't be putting hack-job self-driving cars on public roads. Either do some engineering so that they keep the backup system in place or keep it on a test track. This is Chernobyl-like irresponsibility.
Are you an engineer or at least familiar with vehicle engineering? Do you know for a fact that Waymo/others don't disable built-in safety mechanisms in similar fashion? If not, perhaps it may be best to not pass armchair judgment...
As the vehicle can obviously be operated with the emergency braking system in place, it seems highly implausible that an autonomous system could not be designed to work with it in effect. If Uber did not do so merely because it would have been inconvenient or taken more time or effort, then that would be even more damning than a bad, but well-intentioned, engineering decision.