I think ancestry.com is only part true with results. it’s a business after all, they just want more and more people to pay them money, so they make customers happy or intrigued with results so they tell more people and the money keeps flowing in. Like gambling in a way - you get addicted.
I’ve done ancestrycom and of those I know, I am shocked at how accurate they are. Of those I do not know, I do believe they are my blood relatives.