Interesting. I think it's the opposite. Because PM culture differs from company to company, I feel like companies interview for PMs with a bias for how they expect their PMs to behave. This would be unlike Developers where companies are looking for folks proficient in specific languages.
I've had friends who interviewed with companies for PM positions and the focus was on their doing great UI mockups. The interviewer was looking for good UIs. Unfortunately, these folks were coming from places where the UI mockup they did was just basic placement of elements to communicate the elements they expected their solutions to use. A seperate design team would later turn their mockups into beautiful UIs