Terraform 101 - Non-dependent Dependency

example.tf

provider "aws" {
  access_key = "ACCESS_KEY_HERE"
  secret_key = "SECRET_KEY_HERE"
  region     = "ap-northeast-2"
}

resource "aws_instance" "example" {
  ami           = "ami-983ce8f6"
  instance_type = "t2.micro"
}

resource "aws_eip" "ip" {
    instance = "${aws_instance.example.id}"
    depends_on = ["aws_instance.example"]
}

resource "aws_instance" "another" {
  ami           = "ami-f293459c"
  instance_type = "t2.micro"
}