He's also talked about this on the CoRecursive Podcast:
Andreas: Well, I don’t know that I ever had a real direction with it. But in the beginning, I remember feeling kind of frustrated with finding myself using Linux again and thinking it’s nice to be back on Linux. Everything is snappy. And the developer experience is really great, but I sure do miss having the source code for everything.
Adam: This is a fascinating distinction to draw.
Linux is open source. Everyone has access to the code. But if you listen to episode 70 with Joey Hess talking about Debian, making changes can be a bureaucratic process. And that’s just for one distribution. There are hundreds of Linux distributions. Even if it’s a one line change, it could take years to get that upstreamed and spread into various Linux distributions. If you listen to episode 67 about Zig, that was one of Andrew’s motivations behind creating Zig.
But meanwhile, Andreas has another strategy at Apple. Everything was in one place, and everything was built internally.
Andreas: And when you’re in that environment, it’s extremely powerful.
https://corecursive.com/serenity-os-with-andreas-kling/