I think there are ways to tell by simply asking deep questions about the system someone claims to have built, critiquing the design decisions, diving into why this technology over that technology.

When I've hired or been a part of a hiring process, I always place emphasis on a candidate's past projects and ask deep technical questions around those. I also always review their GitHub repos if one is provided in the profile and I will ask them deep questions about their repos, why they chose this tech or that, interesting pieces of code, design tradeoffs they made, etc.