Yes, the Battlefield 1 beta starting today is fair. It starts today for those who took advantage of a free opportunity to sign up and choose the console on which they will play the game. It will be released to the public tomorrow. It is perfectly fair as it gives people who signed up the advantage.
Yes, it is fair that the Battlefield 1 Beta starts today for only some gamers. Most things Beta are only available to a select amount of people to generate feedback before it is released to the general public. It isn't about fair, it is about business and it is a smart move.
If a company feels like they need to release a product in stages, they have to be able to do what works best for them. Movies come out at different times in different countries, and the companies have good reason for doing it that way. If someone wants to try a product earlier, they need to be a part of testing or go where it is available.
It might not feel fair to some that others get access to Battlefield 1 first, but we can learn life lessons even from the gaming world. The company isn't saying that there isn't going to be an eventual release to every, but the game needs to go through Beta testing first.