"we asked Boeing if they had any objection to this or that and they said no." So a 'not recommended' or some such became an OK if you asked properly.
Not quite - when I was still working we'd often get requests to do something other than the Boeing recommendations. We'd look at it, and if we couldn't find a reason to prohibit it, Boeing would provide an "NTO" - No Technical Objection. NTO is
not the same as an OK - the NTO give Boeing plausible deniability if something does goes wrong (you didn't follow our recommendations, even though we didn't tell you that you had too). While the difference may not be important to the pilots, it's very important to the lawyers.