Hi Chris,
I think you DO need a full assessment from the NZQA for your PR application. Although saying that, I would bet that if you phoned NZIS and asked, they would say the pre-assessment is fine!

It does state in a few places regarding immigration applications, that you will need to have your qualification assessed by NZQA, so i'm assuming this means the full assessment, not just the pre-assessment. Yet another good example of NZIS vagueness if you ask me!