It means you hire folks who can do customer support. That's definitely not an introverted engineer. Sounds like the benefits might even be worth the extra hiring filter.
Introverted doesn't mean anti-social or shy.
I do agree that it is a great hiring filter though: we definitely want to work with people that can maybe step out of their comfort zone a little and get a new perspective on the product they build, and the people that use it. You don't have to be a social butterfly, but you shouldn't need to wall yourself off from your customers, or the rest of the company for that matter.