When did you switch to pair programming? Your post starts by stating you just hired the unqualified dev last month, so did this unqualified dev slip through your pair programming system? And if they did, doesn’t that undermine your view that the pair programming approach has dramatically improved your good hire hit rate (or, if pair programming is newly instituted in response to the unqualified dev hire, how can you claim to have an improved hit rate in only one month of use)?
It’s not necessarily undermined. Presuming the timeline is accurate: large orgs are hiring constantly and, if the person who commented is high enough in the org chart on whatever they consider to be their team, they may see a large number of hires.
Less than a month is not long enough to make the determination that your hiring process is producing better hires in my opinion (unless your old bad hires were flaming out in under a month, I guess).