As Simon McVittie <smcv@collabora.com> wrote on
https://bugs.debian.org/865206 and on the AppArmor mailing list:
"Anything in /var/lib/flatpak/exports/share or
~/.local/share/flatpak/exports/share is essentially equivalent to
the corresponding path in /usr/{local/,}share, and is something
that has deliberately been "exported" to the rest of the system by a
Flatpak-confined app.
The only reason to prevent reading those directories would be if you do
not want the AppArmor-confined app to be able to enumerate the other
software you have installed on your system, as an anti-fingerprinting
mechanism.".
Bug-Debian: https://bugs.debian.org/865206
