Although true, podman did have this feature first, and it's still experimental and unsupported in docker. Docker provides scripts to attempt the setup automatically if you're on a Debian or Red Hat based system, but if you're using something else, you're on your own, and it's complicated and error prone to do, mostly because configuring the daemon and socket to work without root is way more complex than just adding in UID/GID mapping and installing slirp4netns, which is all you need to do to get rootless podman working. It's even easier now that overlayfs works without root without needing fuse-overlayfs, but you're kind of aced out of luck on the docker side with them only supporting Red Hat and Debian, since I don't think any of those get the latest kernels like you'd get with Arch or something you just customize yourself, other than maybe Fedora Stream?