How do you keep from spiraling when an interview loop includes a product manager and you have no idea what they're actually scoring you on

Next round has a product manager sitting in on what I assumed was a pure technical interview. No idea what they're actually evaluating, whether it's how I explain tradeoffs to a non-engineer or something else entirely. Every mock interview I've done has been engineer-to-engineer so I have zero practice reading a mixed-audience room. What's actually being scored in a round like that?