It's explained in the article, security section: b/c installing flatpak can also run arbitrary code as a user. And I won't argue that running malicious code as

It's explained in the article, security section: b/c installing flatpak can also run arbitrary code as a user. And I won't argue that running malicious code as a user is always harmless. Regardless of root access if you're installing flatpak and its author want to pwn you - they can do it even without root access