The "idea guy" is the guy who comes to a developer and start with "I've got this great idea for an app…", thinks it's genius but never dives down to all the details of said-app.
A product person might or might not know how to code but s/he will(/should) be able to articulate exactly what the product should do or not, how things should work together, etc. It's common for developers to think they don't need anybody to make a good product but a great product person will make a difference.
It doesn't matter if they understand how to code or not.
Indeed. That's not their role. Understanding how to code does not a good product make. There are tons of examples of that.
However, you have a point about the industry giving a pass to people with previous successful project(s). But probably with good reason: overall there aren't that many very successful projects, so if you had one, it's still much better than a lot of people.