No, that was not what they said.
They said they wanted to design a real upgrade to the F5, and therefore the best film SLR they have ever built. That is the reason why the F6 is improved so much and in so many regards in comparison to the F5. Nikon wanted to make an even better camera, and they succeeded. I know for sure, because in contrast to you I am using both cameras, also for professional jobs.
People with no market knowledge have misinterpreted one statement in one interview with the F6 engineers: That Nikon expected a change in customer market share, because the market of especially press photographers had begun to switch to digital during the R&D phase.
But that is a different topic, and is not related to the fact that Nikon's R&D target / aim was to design their best film SLR ever, and a significantly improved camera compared to the F5.
Because what people who are doing this misinterpretation don't know is that all so-called "professional" cameras from all manufacturers, 35mm and medium format cameras, were mainly bought by non-professionals:
60-80% (depending on camera type and regional market) of all these professional cameras were bought by non-professionals, so by (enthusiast) amateurs.
That is the reason why these cameras could be designed and introduced to the market: The amateurs financed the R&D. The pure professional market has never been big enough for that. I am working in this industry, including market research. I have the numbers in my analysing tools.
No matter whether nikon F2, F5, Canon F1 or EOS 1V, Hasselblad 500 series, Rolleiflex TLR series or Mamiya RB / RZ 67: The biggest customer / buyer group has always been the amateurs, not the professionals. Example: I visited the orginal Franke&Heidecke / Rollei factory two times,and talked there also to the distribution and marketing experts. They told me that constantly over all the decades about 80% of their cameras were bought by non-professionals. Hasselblad confirmed that for their sales, too. Leica as well. With Nikon and Canon there has been a bit more regional differentiation, but the overall picture has been and is the same.
I know that after the introduction of the F6 lots of professional portrait and wedding, nature and travel photographers bought the F6. And Nikon of course have known that demand. That the F6 was only bought by "rich amateurs" is simply wrong. One of the numerous internet myths.
That was not their intention. Their intention was to offer the best possible film SLR to those who wanted or needed one. No matter whether for professional or amateur use. And at that time still lots of professionals were using film (when Nikon started the design phase film sales were on a global record level).
So Nikon had exactly the same intention with the F6 as they had earlier with the F, F2, F3, F4 and F5: At all time points they intended the best design they can do for all potential customers with their top F-line model.
Same did Canon with their top-line cameras.
No "system" camera? Sorry, you definitely don't know the F6. It is offering lots of system functions none of the other F cameras can offer.
And this "the F6 is not a professional camera because it has no interchangeable viewfinders" is just internet talk of amateurs, camera collectors and gear-heads.
But not at all talk of professionals, because they have abandoned interchangeable viewfinders decades ago. The demand for interchangeable viewfinders had been tiny and negligible, and because of that the manufacturers stopped them decades ago: Minolta was first in the 80ies, a bit later Canon followed in 1989 with their EOS 1, Pentax then a bit later and Nikon were the last in 1999 with the D1. And the others like Leica and Contax choosed the more robust fixed prism viewfinders right from the start.
Fact is that professionals are using cameras with fixed prism viewfinders successfully for several decades. Tell them that they are using "amateur" or "non-system" cameras because the viewfinder is not interchangeable.....if you have luck they will only laughing

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Best regards,
Henning