The Chief Scientist of US Space Operations Command "confirmed that the velocity estimate reported to NASA is sufficiently accurate to indicate an interstellar trajectory" [1] using "additional data available to the Department of Defense" which I assume is classified.
As far as I can tell this paper isn't making any extraordinary claims about extraterrestrial intelligence [2] (which Loeb is infamous for), it's just confirming that the chemical composition - the ratio of beryllium, lanthanum, and uranium specifically - doesn't match any known minerals or alloys in our solar system.
There are thousands of known minerals so it's not out of the question that they're wrong.
[2] The second to last sentence notwithstanding: "Another possibility is that this unfamiliar abundance pattern may reflect an extraterrestrial technological origin."
As far as I can tell this paper isn't making any extraordinary claims about extraterrestrial intelligence [2] (which Loeb is infamous for), it's just confirming that the chemical composition - the ratio of beryllium, lanthanum, and uranium specifically - doesn't match any known minerals or alloys in our solar system.
There are thousands of known minerals so it's not out of the question that they're wrong.
[1] https://twitter.com/US_SpaceCom/status/1511856370756177921
[2] The second to last sentence notwithstanding: "Another possibility is that this unfamiliar abundance pattern may reflect an extraterrestrial technological origin."