Even if they are extrasolar, it doesn't mean anything interesting. Everything in the solar system is extrasolar if you go back far enough, and of course material from outside the solar system arrives from time to time. The interesting thing the author wants so very badly to believe is that these little blobs of melted rock and metal were from some kind of technological contraption built by aliens.
That is not true the composition and material of our solar system are the result of a Supernova remnants. The element composition of each nebula is unique since no star is exactly the same(although it could be quite similar), but outside of the other stars that formed alongside our sun 4.5 billion years ago, other solar systems have different element and isotope ratios.