Nikon maintained the F mount from 1959....not from 1985. That makes the F mount more cumbersome, needing more mechanical linkages etc. The adapter challenge is different. You don't know how much more inherent complexity there is in an FTZ adaptor compared to a Sony A-FE or Canon EF-RF.
Is this a fact about cumbersome mechanical linkages or a hypothesis?
The other factor is lens availability. Sony have only 19 A mount FF lenses, so when the FE system started, they had to have a screwdrive adapter to make the lens range broad enough. Nikon have more than 40 AFS FX lenses supported by the FTZ.
To me it sounds like Nikon simply wants you to upgrade your old screwdriver lenses to the much more expensive new Z mount lenses, -- that's my hypothesis. No matter how much you like those old lenses. I'm yet to see any reason to upgrade, for instance, 85/1.4D, 105/2DC, 135/2DC, or 180/2.8D to anything whatsoever. IMHO, they are perfectly fine lenses in their own right, warts and all. I'm not saying they are fine for everyone, I'm just saying it would be nice if those who think they are fine could continue using them on Z should they so choose.