The AppArmor profile covers the packaged version and the standard privileged install location. You are correct that it does not cover running firefox from an unprivileged user writable location like $HOME.
For unprivileged user writable locations like $HOME/bin/ the user has to deliberately make a privileged action like installing a profile for the location of the application. This applies to the appimage version run out of the users $HOME as well.
The AppArmor profile covers the packaged version and the standard privileged install location. You are correct that it does not cover running firefox from an unprivileged user writable location like $HOME.
For unprivileged user writable locations like $HOME/bin/ the user has to deliberately make a privileged action like installing a profile for the location of the application. This applies to the appimage version run out of the users $HOME as well.