That statement assumes the author has seen the entire universe, inspected everything in it closely enough to make such a bold and sweeping statement.
I believe the universe is infinite, can't offer any proof but if not infinite, what comes beyond that? If infinite, why not an infinite number of possibilities of life elsewhere?
The universe is everything, there aren't two or more of them, no matter what the comic books say, All existing matter and space considered as a whole; the cosmos = universe. Can there be two or more "everythings".
That statement assumes the author has seen the entire universe, inspected everything in it closely enough to make such a bold and sweeping statement.
I think what the author is implying is that there is Zero evidence that life exists anywhere else in the universe. As far as the 'possibility' of life existing elsewhere, anybody's guess is as good as anyone elses.