I suspect the article isn't very well organized. The researcher is quoted further down:

“Some archaeologists were skeptical, as they thought that the amount of nickel found in Bronze Age iron tools was too low to consider them of meteoritic origin,” he says. “But I’m a trained cosmochemist, so I knew the problem was just corrosion. And I was able to show—partly thanks to Morasko meteorite data—that nickel was leached away during corrosion.”

So there were probably multiple issues.