I can tell that you're not a violinist. A certain xkcd [0] comes to mind. Some things are very easy to violinists, and some are extremely difficult. Those things are very easily confused by non-violinists.

You're conflating two things:
 - scenario A, "here is violin A, here is violin B, is B a copy of A or is it the same instrument?": the xkcd analog is "sure, easy GIS lookup, gimme a few hours"
 - scenario B, "here is violin A, here is violin B, which one is which?": the xkcd analog is "gimme a research team and a million dollars"

Every professional could answer the first question with near-flawless accuracy. Answering the second question is extraordinarily difficult, assuming you haven't picked violins that make the question quite obvious. The interesting thing - which may confuse non-violinists - is that this applies to every kind of violin. Cheap, expensive, old, new, whatever you choose. There's a reality distortion field around Strads, and it works both ways. As it turns out, saying "which one is the old violin" is very hard even when it'd seem quite easy.

Violinists, in particular, have large egos (trust me, sometimes they get so big we have to turn sideways to go through doors) and often think they can do things they can't. Some violinists think they can successfully complete scenario B from earlier, but in real life it's very tricky - regardless of what the instruments are, Strads or non-Strads. When someone's writing the article after the "shocking!" "study" gets published, they find one such violinist with a large ego, who is then "shocked!" that they could not identify the Strad. Please note, however, that this is completely different from scenario A.

On the note of copies of violins, there's a story too interesting to not share with HN. There is only one violin that has gotten close to being an exact copy, Il Cannone. Most violinists know its story: Paganini gambled away his priceless Amati violin, and was gifted a neglected Guarneri violin from an amateur violinist. Paganini fell in love with it and named it "my cannon violin" for its sound (Il Cannone). For repairs, Paganini sent it to Jean Baptiste Vuillaume. Vuillaume was the most famous luthier in the world at the time (he even owned the Messiah violin, currently the most expensive violin in the world.) Over decades of repairing Paganini's violin, Vuillaume made an exact copy of it, such that upon initially seeing them Paganini was unable to tell the difference. Later, however, Paganini did notice differences in tone.