They're entirely abstract. Unless you're a professional real estate analyst, you have absolutely no idea what some proposed development is going to do to your "property value" (even then, you're basically guessing).

When you go to planning meetings, people are not generally complaining about property values. They're complaining about neighborhood character, traffic, parking, etc. I'm not going to say it never happens, but when it does, you should dig deeper. There are always real concerns.