Why flatpak copies files to /run/user/1000/doc/

I installed keepassxc via flatpak and noticed that it copied my passwords database from folder that it was before
/home/user/data/password/pass.kdbx
to
/run/user/1000/doc/ee3a8011/pass.kdbx

I also noticed there are some files like jpg that I downloaded from internet via Firefox.

Is it normal? Is it safe that keepassxc puts database there?
Are these folders in this location temporary?

Those files aren’t copied but mounted in virtual filesystem - they’re same files available under different path in order to be accessible for flatpak apps.