Understanding policy attachments?

I’m importing few resources into terraform, I have the following resources:

  • aws_iam_group
  • aws_iam_group_policy_attachment (10 policy arn’s)
  • data_aws_iam_policy_document. (for inline group policy)
  • aws_iam_group_policy (attaching the inline policy to the group)

I have a removed 1policy arn , replaced it with a different arn and imported all these above resources except the replaced policy arn . This replaced policy arn does not exist in group and is a new addition.

But when i run a terraform plan command, it shows that i would be adding my 10th policy but why it’s not showing that it’s going to remove the old policy arn? Why is it showing like that?

terraform plan:

  # aws_iam_group_policy_attachment.group_policy[9] will be created
  + resource "aws_iam_group_policy_attachment" "group_policy" {
      + group      = "xxx"
      + id         = (known after apply)
      + policy_arn = "arn:aws:iam::xxxx:policy/EC2_readonly"

Plan: 1 to add, 0 to change, 0 to destroy.