Would we name a map book "A Toyota Roadmap", as if we don't know that there are other cars, and that a map applies to cars, not just to Toyotas specifically? Sure, a map would be different for push scooters (Windows), but a map would be the same for cars and small trucks.
It seems petty, but it becomes difficult to make a distinction between what's generally Unix and what's actually specifically Linux when we just call everything Linux.