I mean you could read the linked blog post where they explain it

Third sentence:

Flatpak serves as the primary application distribution method for image-based operating systems including Fedora Silverblue, openSUSE Aeon, SteamOS, and GNOME OS. It is the preferred format for major ecosystems such as GNOME, KDE, and elementary.

Great news!

From my understanding it is the same on linux though, theres no sandbox preventing an app or malware from accessing anothers app data

Yep, fork of Element https://element.io/en/case-studies/tchap?ref=element.io