The Container/Dockerfile equivalent of the fedora-toolbox OCI images
installed all languages by removing %_install_langs (set to en_US by the
fedora base image) from /etc/rpm/macros.image-language-conf [1]. The
Kickstart does the same in the %pre section.

Therefore, it's self-contradictory to have '%packages --inst-langs=en'.

The fedora-toolbox OCI image is meant for interactive command line
environments, not for deploying server applications. Therefore, they
need a fully featured CLI user experience at par with what's offered on
Fedora Silverblue and Workstation. Among the Kickstart files defined
here, other than fedora-container-toolbox.ks, only these ones don't
install all languages:
* fedora-cloud-base.ks
* fedora-container-base-minimal.ks
* fedora-container-base.ks
* fedora-container-common.ks
* fedora-eln-container-base.ks
* fedora-server-vm-full.ks

All the other Kickstarts, and definitely those for Fedora Workstation,
install all languages.

[1] https://src.fedoraproject.org/container/fedora-toolbox
https://github.com/containers/toolbox/tree/main/images/fedora

https://bugzilla.redhat.com/show_bug.cgi?id=2244503