The ICRC stated that they couldn't reach consensus and that the Interpretive Guidance provided their own recommendations and does not necessarily reflect the majority opinion of participating experts.

The DPH meeting reports show there was considerable contention beyond the requirement of a continuous combat function or IX. Dissension was significant enough that over a third of the experts involved asked for their names to be removed from the Interpretive Guidance prior to publication which led the ICRC to remove all the experts' names.

Then there are all the papers published criticizing the document for reasons that go beyond just the two most contentious issues, several by experts were among those consulted by the ICRC (e.g. Schmitt, Parks).

Given the dissension, I find it strange that such a document could possibly be widely accepted as the authoritative interpretation of what constitutes DPH by States as you claim.