I'm still saying that treating this like a lawsuit isn't really correct, as "Is this design inherently" unsafe isn't a legal issue, so not answerable by the cou

I'm still saying that treating this like a lawsuit isn't really correct, as "Is this design inherently" unsafe isn't a legal issue, so not answerable by the courts. And honestly if a car company is willing to subvert a safety investigation to that extent, it doesn't really matter if you gave them "unfettered" access or not. If they're willing to break DVSA rules they'll have plenty of chances to do so during their investigation anyway.