Redox follow the Debian packaging design, but it will support reproducible builds and someone can implement immutable/reproducible declarative configuration.
My guess would be that it's not a property of the kernel, it's a property of the software distribution you build upon that kernel. The same way you can distribute software for Linux with Guix, Nix, APT, RPM, Flatpak, I suppose in the Redox world you could distribute software and deploy systems in many different ways.