Bullshit.
I've read Jerry Mateparae's speech, and there is almost nothing in there which is not a basic explanation of constitutional orthodoxy. The processes Trotter finds "alarming" - the requirement for "clear and public statements by the party leaders", for example - have been the practice since they were outlined by Michael Hardie Boys before the first MMP election in 1996. Back then, Hardie Boys laid down the basics:
[T]here is more than a reasonable chance that the election will not result in a clear message on who should form the next government. In that case, I assume that once election night results are known, the political parties will immediately begin the process of assessing each other as potential coalition partners.
I would expect that at some stage, there would be clear and public evidence that the necessary political agreement had been reached, and that a government could be formed which had the support of the new Parliament. That might be in the form of a joint public statement by the party leaders. It might be a fully-fledged coalition agreement. It might be public acknowledgment by smaller parties that they will support a larger one as a minority government.
I stress the importance of the outcome being public. First, it is essential that the people who have cast the votes, know what is happening, and understand the reason for the appointment which I will have to make. Secondly, a clear and public agreement between the parties will provide a firm basis on which I can move to appoint a new Prime Minister should that prove necessary. As in Denmark, this kind of open process enables the Governor-General to be distanced from the political negotiations, but publicly informed about their outcomes. In the past, the "transparent" outcome of the poll provided the basis on which the Governor-General acted. There was no need for advice, from the incumbent Prime Minister or any other sources. There is no reason why this situation should not continue. If the political parties act in this way, the Governor-General should continue to be able to act with confidence, in reliance on unambiguous information already in the public domain.
And that basic message - that the Governor-General will rely on the public statements of party leaders, whether in the form of a written coalition deal or a very public handshake, has bene reiterated (and applied) by every Governor-General ever since. They do not interfere in the process. Instead, they leave it to the politicians and wait and see.
Likewise, Mateparae's comments on the prospect of the largest party being in opposition simply reiterate the point that it is majorities, not pluralities, which determine where the confidence of the House lies.
The only thing which could be considered a constitutional innovation - which passes unremarked by Trotter - is Mateparae's explicit acknowledgement that public commitments to abstain will be included in the assessment of where the confidence of the House lies. But that's not so much an innovation as a making explicit of what we all thought the rules were anyway. Its good that its explicit, but it is absolutely nothing worth losing any sleep over.
Trotter is supposedly one of our country's most senior and experienced political commentators. Its a shame he's such a constitutional illiterate that he works himself up into a state like this. But then, this is a man who approves of coups and electoral overspending to keep the right out of power, so we should hardly be surprised.