I don't know man, the last few stores I've been in had young adults that got to be store directors at 25, and they were absolutely amazing managers. They walked the floor, were understanding, and generally seemed like they knew how to run the business which is all the company cares about. This is one of those situations where age is simply just a number on a piece of paper. Like the post above me mentioned, target employs the persona that they are a young, trendy, yet upscale department store that values youth, and that inconspicuously translates to employees and management.
Now I do not work in your store, so I obviously cannot relate to your experience, but maybe you need to see more of him/her to assess their manager capabilities.
Also, yes. Target often hires managers out of college due to their internship program especially for HR, GM, SE, or SPS.