You assume the person has a clear picture of their childhood home. At least for me I only have very fuzzy mental pictures of my childhood homes, I'd have to try to piece them together to draw anything so I know I'd get many tings wrong. I don't think that everyone adds a lot of fake information to their memory unconsciously, I know some does based on those studies but no study found that everyone did that. Instead I do know that my memory is very rarely wrong, when I answer test questions and I remember something from long ago I am almost always correct when answering for example so I got good grades without studying much at all.
I barely studied for tests and still remembered the questions, the grades I got from them are still there. It is very hard to fake that sort of thing for yourself, everyone knows roughly how well their memory serves them during tests in school. If you had to study a lot then you know your memory is shit, so rationally you shouldn't believe anything you recall.
Edit:
> Do you ever sometimes have mistaken beliefs?
I remember the sources of my beliefs. Sometimes I have mistaken beliefs since the sources were wrong or fuzzy, like my parents told me something that I then believed, but then I learned that my parents were wrong. This makes it very easy to correct mistaken beliefs, since you just go back to the sources and verify and re evaluate the information against the new disagreeing information.
Remembering the sources of what you know isn't that much extra information, so it isn't particularly hard to do, but it helps a lot keeping yourself more rational.
