If Sam would let it go what would happen? Nothing. Criticism and comparisions already exist and will exist. Having it coming from board member at least gives counter argument that they're well aware of potential problems and there is opportunity to address gaps if they are confirmed.
If regulators find argument in the paper reasonable and that's going to have impact - what's wrong with that? It just means argument was true and should be addressed.
They don't need to worry about commercial side because money is being pured more than enough.
The nature of safety research is critical by definition. You can't expect to have research constrained to talk only in positive terms.
Both sides should have worried less and carry on.
That's the pro safety solution.
The optics dont look good though if a board member is complaining publicly.