Services that can utilize the full power of a single machine are quite rare. I have about 15 docker containers in total taking up about 800mb of ram on one of my servers. In reality having multiple can be more complex and harder to maintain, not to mention power efficiency and cost.
I believe this is distinctly different. Fedora Silverblue allows you to install packages through rpm-ostree. The idea Adrian presents is that this overlay system is a band-aid for issues in an immutable operating system.
There are several other differences discussed, but it’s also worth mentioning that because solution A exists, doesn’t mean there can’t or shouldn’t be a solution B.