I have searched on the net and I do not find a big difference.
"He was witnessed by two officials who were official witnesses"?!
There are differences but perfect synonyms rarely exist.
While also not commenting on the Ader incident...
Your English headline has two possible meanings, like the silly example of "Children make nutritious snacks."
I think that Haraka intepreted your headline to mean that Ader flew, but did not do so in front of "official witnesses." In other words, that you were implying that his alleged flight was suspicious or that the witnesses had zero credibility because they were not official.
I suspect that Haraka thought you were drawing a distinction between "official witnesses" and mere "officials."
I believe the intended meaning of your headline is not only did Ader fail to fly, he dramatically failed to do so in front of "official witnesses."