Nikon, as I have seen especially in the US, has taken a lot of flack/heat/griping, the past few years from non NPS members who watched NPS members order the same products later but get them much sooner. Recently, with the Z8 and now with this 180-600, Nikon seems to be holding back the release of products until a large number of units can also make their way into the hands of non NPS members in the first wave of released products.
I doubt Nikon undercounted the demand that would come from non NPS members as this consumer grade glass has been sitting on the roadmap for multiple years and was constantly discussed and wanted by the masses. But I‘m not surprised they underestimated the numbers of professionals who would put in NPS priority requests for a consumer grade zoom covering 400 + mm worth of distance and is f/5.6 at its brightest range of 180 mm. What imaging executive would bet his or her job that a professional would want a 180 mm f/5.6 lens?
It would be a bad look if Nikon released the 180-600 and the only people getting them early on were NPS professionals. That’s a look Nikon wants to avoid at all costs. And the cost may very well mean September shipments to consumers of all sorts.