Maybe. But they, and many others overestimate the amount of size flatpaks take up.
Flatpaks use a "runtime", a shared set of libraries and programs flatpak apps use. With one flatpak app, there is just one runtime. But with 2, 3, 10 flatpak apps, there are still only going to be 1 (to 3) runtimes on the system. This is not the same for something like appimage.
In the blog, they compare the size of deepin calculator across formats. But this is not a fair comparison. A more fair comparison would involve comparing the app size without the runtime, or comparing many apps installed.
In addition to this, if you are on btrfs, further deduplication and compression is done. This (and symlinks) won't show up in many disk and space usage analysis tools. To get a more accurate measure, use compsize instead of traditional tools. It will show you how much transparent compression (when btrfs compresses files but you can stilll access them normally), symlimks and the like are saving space.
Anyway, I am interested in more cross distro package managers though. Flatpak, docker, and nix cover a lot of things but have their annoying edge cases and paper cuts, especially in comparison to snap in some ways for some apps.
Edit: linglong appears to reuse system libraries, which would probably lead to significanr space savings at the cost of portability across distros

