>To preload container services in a pool, you must do it via the Databricks API, since this option is not available through the UI.

I'm not trying to "preload" it, I just want to my cluster to (1) use a container, and (2) use my pool. I'm aware that the create instance pool API offers a "preloaded_images" mechanism, but there's nothing in the docs that says "preloaded_images" are *required* if a cluster create request uses the docker_image option. Can you clarify?