The toothbrush bot army story got started by a Swiss newspaper writing about a scenario they heard from a cybersecurity company and claiming that even though it sounds like a Hollywood movie, "this really happened". When the company in question was reached for comment, they said it was hypothetical.

In the end, the story's spread can be explained by a journalist's simple misunderstanding that made the story much more virulent.

In this case, the journalist probably also doesn't understand the technical details, but we have a link to the researchers' own write-up right there in the article, which makes it much easier to rule out simple misunderstandings. So the situation is completely different.

That said, they're not reconstructing the fingerprint ridges from the sound the way you're probably imagining. Instead, they build on an existing attack exploiting fingerprint readers' error tolerance with a set of "masterprints" that are unusually likely to be accepted as a match, and the sound is used to determine which masterprint to use first.