I don't even mean domain knowledge so much as an intimacy with the stack, the tools ... and not even so much 'knowledge' but 'know-how'.
I work with a company that sells IP in the form of patents, but it's only 1/2 the value. You have to know how to use the components, and the resulting data and finesse it.
The engineers who are a class above the ones who rely on 'domain knowledge' aren't limited by the stack or the tools. They can switch to a different stack and the tools aren't so important to them.
For example I move faster on servers with ssh and tmux. I can do multiple things and configure stuff and test things really quickly with these tools.
A 10x engineer doesn't have patience learning about tmux and he doesn't need it.
In fact if you ever actually seen one of these guys (and they are rare) they actually tend to move slower with tooling. They just use the default terminal app on the Mac, they don't download iterm, tmux, neovim, vimplug or zsh to take their tooling to the next level.
I would even go further to say because they are so efficient they lack the practice needed to get fast with tooling. Other engineers take a more brute force approach and thus as a result they get really familiar with the tools. 10x people don't have the opportunity to practice because they find the solution on their first try.
I work with a company that sells IP in the form of patents, but it's only 1/2 the value. You have to know how to use the components, and the resulting data and finesse it.