Agreed.
A while ago, the NZ government instructed INZ only to give very short deadlines, in the belief that this would speed up processing. In reality, INZ COs understand that people can't magic up evidence in no time flat, particularly if it involves having to get a response from third parties, or getting original documents sent from overseas, so if an applicant gets in contact before the deadline to say what they have done about getting what is required, and showing proof (such as copies of emails sent and received), they will normally allow a reasonable amount of extra time without difficulty. However, if the applicant doesn't make contact, and doesn't supply what has been asked for, the CO has the right to go ahead and assess the case WITHOUT the proof that they felt was necessary, which would probably mean a negative outcome.
If you've missed a deadline, or think you will, get in touch with the CO as soon as you can, and you may be able to rescue the situation.