I have no idea how that connection came about. Would like to know though.
As commented some parts of the story are unclear. I believe there is a reason. If the information was public it would have been there. There is a reason the information is not there. The information Fortis is willing to share is in the book. I can only assume they do not want to share more detailed information.
The Cosmonauts started out with the 5100, white background day/date and white skeleton hands filled with Tritium, tachy bezel.
There was also a version with indices instead of numbers, do not know if that version preceded the above version or the other way round.
Then came the "standard" version 5100, all Tritium covered hands, tachy bezel.
The countdown bezel variant was called the pilot version in an old Fortis catalog, the count-up bezel was called the diver version by Fortis. The tachy bezel was called the cosmonaut version. The GMT/countdown bezel is not in that catalog, so I do not know that name.
Some time later the 5100 was replaced by the Valjoux version(s).
The reference numbers do not make it easier as different models sometimes share the same numbers.
The day/date and GMT models are spin-offs not used in space.
I asked a cosmonaut (the Dutch one) what the deal was with Fortis and he said they were given a Fortis Cosmonaut set during training. If you want you can use it. If you want to use a different watch you can but the Russians have to approve it.
I have the:
5100 pilot bezel (United Arab Emirates Air Force logo on back)
5100 Andora black dial (white dail and hands in the box )
Valjoux tachy version with a faded to grey dial
Blue dail GMT
the day/date
B-42 Ti day/date
B-42 Ti Valjoux crono
I am at work, so no pictures to back it up.
This is what I believe to be true, as a collector and space enthusiast.