To who?
Boeing only needs to report details to the certifying agency and not to the public or its competitors
This.
That fact that some information finds its way in the public realm does not suddenly compel an applicant or authority to explain or justify the outcome of a certification test. I've witnessed many certification tests, both as in interested person, and a delegate of the authority. Some of the tests were not a pass, and some test articles were broken - that's the nature of testing! If a structural element failed at 99% of its predicted ultimate load, hats off to the engineers! A little redesign, with apparently valid design assumptions, and the product should be great. We can hardly have efficient aircraft when the structure has a capacity many times the ultimate load cases - it'll be needlessly heavy.