People Science is not just an upgraded version of people watching, nor is it any field I have ever heard of someone getting a PhD, as that would be anthropology or hominid biology.
Instead, People Science is a method for businesses to gain insight based on data and analytics reacting to how people interact with a workplace and how they best work. Companies that use proper people science tend to have less turnover or internal entropy.
It gives the company a step up in providing benefits and managing how people work and how the workplace affects them.
For example, I recommend paying for a building with electricity. You could use a printing press, but printers tend to work better in today’s market.