There’s very little about reality TV that’s true to life. And this really shouldn’t be news to any of us. There’s no way Rick, Corey, Chumlee, and their “experts” know everything about everything the moment something comes into the shop. Of course, they have to research it—a process that can take months—before spewing some grade-A knowledge.
In the case of House Hunters, the couples we see on TV aren’t actually looking for a house. According to the OP, they already purchased the home. The other houses they’re checking out most likely belong to friends or strangers who want to be on TV.