That is a strange title / comparison. Docker images (even slimmed down) have an OS (most likely a Linux distribution), some libs and the runtime needed for a programming language. On it's own a "game engine + WASM binary" is not comparable.
Seriously, this is a ridiculous comparison. It's apples to oranges.
This site used to have interesting technical discussions, but now its all either AI cheerleading, or vibe coder blog posts.
Maybe it's a good reminder to _not_ bundle an entire OS in a Docker image
Container images don't need an OS. You can always do "FROM scratch" and only copy what's needed to run the binary. If it's completely self contained one executable is enough.
The O/S is provided by the container-host (which is usually a linux VM).
This doc describes building an image from "scratch": https://docs.docker.com/build/building/base-images/#create-a...