Earlier quoted context omitted.
We accept any kind of code, be it a kata made during a workshop or a side project... really we just want to talk about code that the candidate wrote previously. It doesn't need to be large to have interesting tradeoffs made
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…
Finally we are not looking for any specific profile, but so far almost every person found a piece of code to share from their career. We don't get thousands of applicants, so maybe we're not seeing the issue just yet. If it turns out to be a problem, we'll change the process :)