Why? You already gave the candidate a "take home assignment". That assignment should involve interesting trade-offs. If it doesn't, tweak it until it does. Why not discuss that code?

I'm the kind of guy who still likes to code on the side, at home, for fun, after all these years, but I'm also aware that not everyone is like that. Maybe that's one of your filters -- maybe you're looking for people who prefer coding to be 90% of their lives -- but that would be a big red flag in my book. I've seen too many companies who think that they are entitled to employees who will give them everything for next-to-nothing in return.