I understand where you're coming from. They didn't
choose that number! It was chosen
for them by Amazon! It's on Amazon for not
actively forcing users to consider what level of confidence they want to use. Amazon can, should, and I think is perhaps even morally obligated to make customers
actively choose a confidence level.
Yet, might there not be other factors to consider? Bear in mind that this isn't pushbutton easy off-the-shelf. Some actual work is required here. There's probably a batch of Python scripts sitting around that did the work. The most charitable assumption is that whoever did this at the ACLU didn't look at how the tool under examination should be used at all and missed everything about confidence levels in whatever few docs they did read. Under the ACM code of ethics, I am comfortable calling that an unethical degree of incompetence and carelessness.
A less charitable interpretation is that they knew and didn't care because it produced the result they wanted. This is similarly unethical, in my mind on a level with the sort of p-hacking prevalent in social sciences.
You're completely right! They just used the default. It's just perhaps possible that there might be other factors worth considering.