Earlier quoted context omitted.
Yeah, if you are willing to buy that they have something stored they can't identify, this is the most logical explanation. That said, I would still buy that there are probably almost no materials that we couldn't at least get a handle on. If they were truly incomprehensible it would likely be because they were the result of manipulating properties that we don't even know exist yet (higher dimensionality, etc, whateve…
A Pentium chip would probably seem like an incomprehensible material to Alan Turing (and not just because of the awful instruction set), because even though all the materials were known at the time, the design and fabrication techniques and mind-bogglingly fine granularity and complexity of how they are combined hadn't been conceived of yet. I agree the reporters probably flubbed the word "alloy" for lack of a better…
There's no mention of what properties these materials are supposed to have, much less that the materials seem so exotic as to be beyond comprehension or a more accurate description. The original New York Times article merely mentions the "storage of metal alloys and other materials..."
"Alloys" may literally just mean "alloys."