It's fairly standard Physics jargon. Physicists don't like saying the word "impossible", because there's always someone out there that can't stand hyperbole.

It's fairly standard Physics jargon. Physicists don't like saying the word "impossible", because there's always someone out there that can't stand hyperbole. So they often refer to something as "not likely to happen within the age of the universe" rather than "impossible", hence the 13.8bn year estimate here.