I find this sentence quite revealing. The issue here isn't "Testing". When you sell seats to passengers, you are no longer testing. Plus, the whole statement of oversight being "anathema to rapid innovation" is also intriguing to me. And, to compare to Space-X is also interesting. The hurdles of going down to (as I understand) 380 atmospheres is infinitely more difficult than going into micro gravity and air pressure. Plus, as several engineers have stated, including James Cameron, the process of going back and forth, multiple times, to that amount of pressure is going to have a high likelihood of making the vessel unusable. Even before those comments came out, my feeling was that it was probably a somewhat "disposable" vessel, with a distinctly limited life span. The fact that what people like Cameron and others who understand the complexities of this predicted is exactly what seems to have happened kind of shoots down the argument they posted on their web site.Bringing an outside entity up to speed on every innovation before it is put into real-world testing is anathema to rapid innovation.
My gut feeling is, yeah, they signed the waiver, but that's not the end of the story. As has been pointed out, these are billionaires, and they have attorneys. My suspicion is that they will do everything they can to find evidence or proof of contradictory statements about the safety of the vessel. I suspect they will find something to make it at least challengeable. It'll probably take years, and whatever comes of it will probably be confidential.