This is what the article is saying: But modern measurements of troctolite 76536, and other rocks from the moon and Mars, have cast doubt on this story. In the past five years, a bombardment of studies has exposed a problem: The canonical giant impact hypothesis rests on assumptions that do not match the evidence. If Theia hit Earth and later formed the moon, the moon should be made of Theia-type material. But the moon does not look like Theia — or like Mars, for that matter. Down to its atoms, it looks almost exactly like Earth.

While I suppose this is physically possible by chance, I think it is unlikely though. Inner planets do not have moons - Mars' moons are captured asteroids, Mercury and Venus have none. Why would a planet form with a significant mass "partner" in this particular location and not elsewhere in the inner solar system? Some sort of major collision is more likely.