The NRO is essentially just a brand the five RIRs use when they want to make public statements of this sort. So read this as a statement from the CEOs of these five orgs.

With this request, I suspect they are more concerned with ensuring proper processes were followed within ICANN rather than the outcome. I think they are primarily concerned with maintining trust in the wider "Internet governance ecosystem" (that they are a part of). This is a concern as there is greater pressure from governments that want to make the case that the current model is not working and should be reorganised along UN/ITU terms.