Is KEYCLOAK_IMPORT still supported?

The docs for this chart at https://repo1.dso.mil/big-bang/product/packages/keycloak/-/tree/main/chart#setting-a-custom-realm claims that KEYCLOAK_IMPORT is (still) supported, but Keycloak Quarkus abandoned support for this method of importing a realm. Is it actually supported by registry1.dso.mil/ironbank/opensource/keycloak/keycloak or is this stale information in the readme?

Additionally, the examples around --import-realm are confusing. At https://repo1.dso.mil/big-bang/bigbang/-/blob/master/docs/assets/configs/example/keycloak-prod-values.yaml, it is stated,

--import-realm is not recommended for production/operational environments

Okay - fair enough. But then in that same example, /opt/keycloak/data/import/realm.json is mounted into the container, which is seemingly ignored.