This question is really to determine how effective a freelancer is at communicating. A good freelancer over-communicates around deadlines. Shit happens, and sometimes they'll miss one. Hire someone who will give you sufficient notice and explain why and when the deadline will be met.

This is also an important question for anyone working remotely, as communication is crucial to remote work success. You need someone who's comfortable speaking up through Slack or HipChat and who will ask for a call when they need answers quick. You'll be able to glean how comfortable and confident someone is working remotely from this simple question.