"terraform import elasticsearch_opensearch_ism_policy.cleanup ism_policy_id" returns "Import successful!" but actually nothing isn't being added to the state.
All the rest actions work well - add, update, and remove. The state is updated appropriately.
It was tested on AWS OpenSearch 2.3 Service software versions "R20221114-P5" and "OpenSearch_2_3_R20221114-P6".
Thanks!