The headline misses the real controversy - they tried to cover up the incident and only reported what actually happened after the government came back and asked questions, because the reports from first responders didn't line up with what Cruise themselves had reported.
There are also rumors of internal people who felt the cars weren't safe, with a list of scenarios they didn't handle acceptably. The cars really should have had human safety drivers ready to override the car while fixing those issues.
They might want to, but it's illegal.
The "quiet period" is a reference to an SEC law that forces any company to be radio silent for a strict 40 day period during the IPO process. Reddit is in that period now and therefore they cannot say a word.
JPMorgan was fined almost a billion dollars for answering questions on a phone call during their quiet period.