Oh, my poor head! I've sworn off flatpak until now because it took up so much disc space, and now you're telling me it uses extradimensional file storage like some kind of TARDIS system?
No, that is about file system, not Flatpaks. Sure Flatpaks also use shared dependencies, but btrfs pushes it even further. I also avoided Flatpaks until switched to atomic distro, where flatpaks are primary way of installing apps. Common distros do not need them really, until you run some old Debian lol and you want newer software.
What distros are you talking about? Even if install all available DEs, any distro will take ~10 GiB or a bit more. Default installation is much smaller.
I remember at the past my allready running distros were always 20-24gb. With allready most apps installed. Like Mint and Workstation. Maybe my memory is not that good and I am wrong.. I actually can not say how much is my current Silverblue now, somewhere around 20gb.
What I wanted to say, Flatpaks sure pull dependencies, but with lots of Flatpaks your next app will be small, like 2gb or maybe 800kb. With atomic distros Flatpaks make even more sense.
There's no any magic that could reduce Silverblue size, it is based on the same packages as Workstation. Only the installed subset of packages can differ.
Like gnome-tweaks, if you install it in toolbox, it will pull 300mb of dependencies and once installed it is 900mb. Is it magick or 900mb less? Gparted is also missed in Silverblue and not available as flatpaks. Also some magick or anothe MB's?