You are probably right but without all the context here one might counter that the concept of authenticity should feature predominantly in this kind of document regardless. And using a consistent term is probably the advisable style as well: we probably don't need "constitution" writers with a thesaurus nearby right?

Perhaps so, but there are only 5 uses of 'authentic' which I feel is almost an exact synonym and a similarly common word - I wouldn't think you need a thesaurus for that one. Another relatively semantically close word, 'honest' shows up 43 times also, but there's an entire section headed 'being honest' so that's pretty fair.