All database instances within an AWS Aurora cluster does not have the same accessibility.
In AWS Console -
In Terraform -
References:
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_CommonTasks.BackupRestore.html
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/rds_cluster_instance#publicly_accessible
https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/db_instance#publicly_accessible