Flatpak file-picker security issue

I have 2 applications that use GTK for file picking, namely Librewolf and chromium. Librewolf does not have access outside of ~/Downloads, and for chromium I disabled all home-directory access using flatseal, which I confirmed with flatpak enter that I am not able to see those files.

Although that is the case, when picking files (using Ctrl+O) I am able to see and open any file on my system, which is very concerning.

I am on NixOS 22.05 with flatpak from the same branch (services.flatpak.enable = true), but I was not able to reproduce this on another flatpak system with Fedora silverblue. I’d like to know if anyone else has had this issue, and if not, how I would go about securing my system (or ask in another place).

Thanks in advance