Not a judgment about whether it was for better or worse, but I'm curious about this. I think my parents were honest about many things, but here are a few things they didn't tell me at the time, for very good reasons, some of which I only found out about as an adult:
How bad things were between my dad's parents, before their divorce. Although I knew and loved those grandparents individually, I never saw them together; I just knew that I was not to mention one to the other. My dad later said that as he had been brought up on conflict, being married to my mum made him calmer over the years.
That my parents were planning to relocate a very long distance, and had packed me and my brother off to a friend for an overnight stay, while they visited the house we might have lived in. This move never happened in the end.
That on a residential trip with a youth group when I was six, some of the teenage helpers were doing what teenagers do, in the children's dormitories (in the daytime, while the children were busy doing other things): this was in the 1980s, long before safeguarding. My dad was a helper on said trip, and he said that some of the children knew what was happening; but I knew nothing about this until many years later. He also cut the trip short because of this.