Software engineering is a pretty unique field as far as self study goes. There are others since the dawn of the internet, but many domains dont have great online learning resources. And then there's labs and research.
The difference is that software engineering more or less doesn't use a comp sci degree to gatekeep.
Software engineering's main difference isn't even the lack of credentialism, though that certainly helps. The big thing is the core feedback loop of coding. It's short, has immediate feedback, and practically everything you need to become a good developer is freely available due to FOSS culture.