Dogs are like people in that childhood trauma never really goes away. If a dog was mistreated at any point in their life. Even before you owned the dog years ago, it could manifest in aggression.
We had a dog growing up, medium sized poodle mix, that we had adopted at one year and were told had been abused by the husband. Not typically an aggressive dog. However certain unfamiliar men, not all men, but some skinny, white men it seemed were liable to be met with aggression and family guarding behavior.
Every dog I have raised since puppyhood, including a 115 pound mixed breed and a 100 pound husky have had zero aggression issues. That is not to say one can be careless. There is always the chance, and you have to have the space and be able to handle any dog you own.
As a consequence of this, I became accustomed to immediately assessing the aggressiveness of the dogs by eye gazing upon approach, and found the vast majority gentle and sweet. So I get the frustration of their owners, esp ones who take them in as rescues as the local shelters are flooded with them. 9/10 of these animals will probably go through life showing no aggression and live life as wonderful family pets.
But all these excuses about how it’s the owners fault in how they raised them, that there is no official breed, etc, etc... is bs hand waving. These dogs can be dangerous like that pet chimp who ripped that woman’s hands and face off. There is something instinctual in them, and the physical ability, to do real harm.
As to other breeds that can be worrisome, generally bred for protection, such as dobies, rotts, and German Shepard’s, I never sensed the fear that one of those would instantly end the life of my dogs within seconds. Pits and mixes - easily a “holy shit that was close” encounter in the triple digits, probably once a month on average throughout their lifetimes. Far too many situations where an owner had trouble controlling their dog and they got dangerously close.