FNP does not have any logic to differentiate between Elastic or public IP assigned to the AWS instance. The functionality will fetch a public IP address if an elastic IP address is not assigned to the AWS instance. It is publisher's responsibility to ask their end customer to assign an elastic IP to the AWS instance if required.
More information has been mentioned in the FNP provided docs like White Paper: Understanding Virtualization Features in FlexNet Publisher. Customers can share the same information with their end-users.
Note: Another ec2 instance hostid option that is widely used and well trusted by our customers is hostid VM_UUID.