The Nikkor Z 28-75 f/2.8 is almost certainly Tamron, and the new 17-28 f/2.8 seems to be as well. After more thought, I don’t think the 180-600 is though. I haven’t really looked at the new 70-180. The 180-600 has the programmable ring and button, which makes be suspect it’s a Nikon lens.I was actually thinking and gonna suggest that as well at first, but they do seem just diff enough. Tamron's 150-600 isn't an internal zoom (and grows much longer than that Nikon housing looks). Does Tamron actually make a 70-180 f/2.8 like that one?
Also, Tamrons (like Sigmas) seem to have a slightly different color bias than Nikon glass AFAIK, which may be noticeable enough if Nikon's just rebadging/recycling Tamron glass. I'm not sure Nikon wants (to have) anyone to think they're just rebadging 3rd party glass -- well, pretty sure they don't want that even if they're actually doing it...
Then again, this is all new territory for Nikon I guess, including seemingly playing catchup (whether real or just perceived) in this increasingly difficult market...
_Man_