I must agree with you in that I do see both the Z6 and Z7 prioritising existing F-mount users.
However what you should also consider is that many aspects of catering to F-mount users means a continued evolution of a very matured system of body ergonomics, user interface as well as photographically important functions.
Things like the EVF experience. Specs alone doesn’t tell the story and you’d really need to experience it to decide whether it is important to you. For this level of camera, it is of vital importance to me.
I guess you will need to decide on what specs are relevant to you but if I catch your drift, you are saying you’re only starting your photography journey so you may not know, yet. Or do you mean you’re just new to mirrorless?
The good news is there’re almost no wrong decisions and they’re all really incredibly capable cameras, and my bet is within about 2 years you’re gonna see four incredibly capable systems in FF mirrorless even though all but one system are just starting out today. You’ll develop muscle memory to whatever your chosen system is and the question of ergonomics will largely become moot.
My advice is to pick one and stick with it. Unless all you do is buy a kit lens. In which case switch all you like
And a bit of fun. At the risk of overgeneralizing, my prediction is that:
Sony will lead in sensor tech
Nikon will lead optically
L-mount will provide the most variety of differing niches. Luxury, video, quirky Fovean etc.
Canon will lead overall