> because Flatpak was designed from the ground-up to be vendor-neutral
Even if you look at the terms used : https://snapcraft.io/docs/core/store :
"The main way of distributing snaps to snapd systems is through the Ubuntu Store"
So indeed there is the "other store" section which mention you can host your own store but it's clearly not emphasized.
Even the term of Snap "store" vs Flatpack "repo" seems to indicates a more decentralized/agnostic direction of Flatpack.
On flatpak.org/apps.html you can see LibreOffice hosted by documentfoundation.org and MonoDevelop hosted by mono-project.com. They're not all hosted by their respective foundation/website, but still it kinda seems like it is the direction flatpack is pushing for.
So "technically" they all are distro-agnostic, but in terms of distribution system one is pushing for a centralized Canonical-hosted store while the other seems to be going towards a "each foundation will host their app"
This isn't actually a good analogy, because Flatpak was designed from the ground-up to be vendor-neutral. For example, the "runtimes" that provide the virtual Linux distribution for applications to work in are built with packages and tools from the Linux Foundation's Yocto project. Similarly, the code is deliberately hosted on GitHub with no CLA so that all contributors are on neutral ground (there is at least one Debian developer involved). The main developer is a Red Hat employee, and could have used Fedora or CentOS packages, tools and infrastructure, but explicitly chose not to do that, to protect Flatpak's neutrality. He also builds Flatpak for Ubuntu, Arch and other distributions, so that people can freely use Flatpak on their systems even where it isn't currently supported by their distribution of choice.