Approved data means no field approval. Acceptable data, or a basis for approval, generally means an ASI has to sign it. But if you get a letter from an ASI allowing a differnt interpretation, you are probably golden.
You can mail anything you want to OKC - they just file it, probably using temp workers or something. My FSDO used to review my 337s, and would often pick up minor errors. They refuse to do that now. It is a strange form - you have to sign and date it twice. They want to be sure you are sure. Or something.
So if you choose to interpret aomething in your favor - say, like the word "basis" in a document that says it is approved data if you do exactly as it says, and send the 337 to OKC, then nobody will probably ever challenge you - even if the rest of the world disagrees with your interpretation.