Yes, you're correct. Hiatal hernias are often incidental, meaning that they exist but don't really have anything to do with the symptoms or problem. Most people with a hiatal hernia never know it or don't know it for years until they get old and their body starts wearing down.

You had a scope and it showed no hernia. You don't have a hernia. Get another scope if you want but it you had a hernia they would see it. The only way they would miss it is if it's a type I (sliding) hernia, and guess what? Those don't cause symptoms. Only the paraesophageal hernias where the stomach is stuck permanently above the hiatus create symptoms/need surgery sometimes.

Sometimes bodies just do weird stuff.

You say your doc said that hernias from heavy lifting are rare, but that he sees them on scopes all the time. Okay, so how are those two things related? Most people don't lift heavy weights. Just because he finds random hiatal hernias in his patients doesn't mean that his original statement about them being rare from lifting is untrue.