There is an upcoming deprecation of the v1alpha2 apis for inference services in the next release of KFServing.
See: https://github.com/kubeflow/kfserving/issues/1618
inference service v1alpha2 version should no longer be used after 0.6, we should remove v1alpha2 version support from crd and corresponding webhooks, controller and api types. Currently there is a Conversion webhook installed to automatically convert v1alpha2 inference service to v1beta1, although it is recommended rewriting all your spec with V1beta1 API as we plan to drop the support for v1alpha2 in later versions.
The biggest thing we'll need to change is the api type at the top of crd, and then the name 'custom' is just 'containers' now.