You can be sued (in the US) over anything. They could certainly be sued for screwing things up without even any public evidence, but as you point out it's diffi

You can be sued (in the US) over anything. They could certainly be sued for screwing things up without even any public evidence, but as you point out it's difficult to prove gross negligence, so most people won't bother. But certainly it becomes much easier if you have evidence from someone inside the company. YOU don't really need to see how they could be sued, or how an engineer's comments could put them at risk, in any event. If Google's legal counsel believes it to be a risk, then that COULD be what's going on behind the scenes. And this is exactly the kind of thing that a lawyer would advise, which is really my only point.