I can agree with the idea that few people are totally self-taught but I see things differently.
When I think of somebody being "self-taught" I consider that the bulk of their education was self directed. They might have taken a class or had a mentor but they didn't follow a set curriculum. They took a class, followed the guidance of a teacher or mentor but the majority of their knowledge comes at their own decision, not from a prescribed course of study.
When I think of somebody being "educated" in a subject I consider that they took classes and followed a course of study laid out by, for instance, a school of photography or in a major/minor in some other curriculum.
Therefore, I would say that people like me who took some classes, had a mentor and/or learned on their own by reading or self-experience might be better described as autodidacts.
I consider myself an autodidact.
When people ask me what "autodidact" means, I tell them that an autodidact is a person who picked up a dictionary and looked up the word "autodidact."