This is not theoretical. When the openssl fiasco hit, I worked in a place under financial regulation. Not even the defense sector, which is under much stricter rules. We had to go through all logs to ascertain customer data was intact, and since leaking private keys did not leave a trace in the logs we then wiped clean all systems these keys secured.
This was a massive undertaking to coordinate and minimize downtime for customers but it was deemed necessary to comply with security regulations. To hear that a big juggernaut such as Microsoft doesn't even do this without facing much consequences is mind boggling. I can not understand how that would ever pass an audit.
I have literally done incident response I am well aware of what the investigation process is like.
"The box" in this case is their entire org.