Of course, if a developer comes with experience and personal references from acquaintances, you don't need to test their abilities at all during the interview process.
For example, I hired a backend developer last month. She already had the job because she came highly recommended from a trusted friend of mine, but she didn't know that. Here's how the interview went down:
Me: I see on your resume that you've achieved Grand Master level in Microsoft Solitaire Collection.
Her: Yes.
Me: Well, we won't waste any more time then. Welcome to the team.
Same here...except I tell up front when they apply that it's more of a formality for HR. I respect their time and don't want them to waste time preparing or getting nervous. I tell them it's mostly for the team to get to know them and for them to evaluate the team and we'll keep the interview light.
I still give my team the option to decline them if there's major red flags - but I have not had that happen.
Also, a reminder...an interview it is a 2 way street. Your 1 question interview doesn't give the candidate an opportunity to interview you or your team and the "Welcome to the team" is a little presumptuous...I assume it was left out for dramatic effect and I'm sure (I hope?) you allowed the interviewee time to ask questions.
Completely off-topic: I am 99% certain that I read a very similar comment on HN a few weeks back. Did you happen to share this anecdote on another HN thread?
For example, I hired a backend developer last month. She already had the job because she came highly recommended from a trusted friend of mine, but she didn't know that. Here's how the interview went down:
Me: I see on your resume that you've achieved Grand Master level in Microsoft Solitaire Collection.
Her: Yes.
Me: Well, we won't waste any more time then. Welcome to the team.