This statement is a bit misleading. I assume the author is describing the Schwarzschild radius which is the radius of the boundary of Black hole. It is commonly known as the event horizon.
The event horizon is the boundary defining the region of space around a black hole from which nothing can escape, not even light.
Under General Relativity, a non-rotating black hole is contained in a region of infinitely small volume, where the curvature of space–time is infinite.
I did read “A Brief History of Time: From the Big Bang to Black Holes”, but it made my brain hurt.
That said, writer Wilczek is a very sharp cookie, I doubt he would need to mislead you.