Just reading the blog article, I figured half as much
Most basaltic meteorites come from large parent bodies, like Vesta, which have evidence of differentiated layers within these objects. Essentially, they've been large enough to allow different rock types to form within them via total or partial melting of their internal structures. Usually, asteroids large enough to do this have also undergone hydrostatic equilibrium and so are round. They're also mostly type S and associated asteroids...basically made up of silicates and metals, much like a tiny version of a terrestrial planet.
The meteorites come from collisions of other bodies with these asteroids.
