Well, this is true, but it's also hyperbole. It's not really everybody misunderstanding the problem so much as simply not caring. People are sloppy with the terms "NP-hard" and "NP-complete" and use them interchangeably because it's usually not important. Usually they mean "NP-hard", and that is the significant thing.

Yes, it's wrong to use "NP-complete", but plenty of people who thoroughly understand the problem do so. Welcome to Computer Science, sloppy is par for the course.