This _is_ Silverblue and other ostree-based repos.
This article is focused on containers because when the root OS is immutable, then mutable developer workflows/etc necessarily happen in containers (distrobox, toolbox, whatever). OSTree is/was commonly described as "git for filesystems". Every update is an entirely new system image which applies a 3-way diff. It's possibly to state in a single command "show me the drift in my config files/data versus the ref I'm running" and/or "show me the diff between my running system and an update I may apply".
This article is focused on containers because when the root OS is immutable, then mutable developer workflows/etc necessarily happen in containers (distrobox, toolbox, whatever). OSTree is/was commonly described as "git for filesystems". Every update is an entirely new system image which applies a 3-way diff. It's possibly to state in a single command "show me the drift in my config files/data versus the ref I'm running" and/or "show me the diff between my running system and an update I may apply".