I am not an expert, but my understanding is this is at least partially correct. As mentioned, asteroids are differentiated core fragments, and impact craters (eg Chicxulub) are sometimes dated by the iridium distribution in geological layers. The iridium comes from the asteroid. I don’t know why iridium gets all the press over other other platinum group elements, but a cursory search suggests they’re also used for impact dating. https://physicsworld.com/a/iridium-in-undersea-crater-confirms-asteroid-wiped-out-the-dinosaurs/