When setting up Zitadel, why is the default adminuser called `zitadel-admin@zitadel.localhost`?

When setting up Zitadel, why is the default adminuser called

zitadel-admin@zitadel.localhost

zitadel-admin@zitadel.localhost

instead of

zitadel-admin@localhost

zitadel-admin@localhost

?

I'm setting it up in my Kubernetes cluster, running Zitadel on domain

zitadel.local.k8s

zitadel.local.k8s

and then the username becomes

zitadel-admin@zitadel.zitadel.local.k8s

zitadel-admin@zitadel.zitadel.local.k8s

. How to get it to simply be:

zitadel-admin@zitadel.local.k8s

zitadel-admin@zitadel.local.k8s