Can you help us out by showing which ones you mean?
On the Fortis website, the B-42 Official Cosmonauts is a three hander:
View attachment 483646
Then there's the Official Cosmonauts Chronograph:
View attachment 483645
And then there are "classics" of the chronograph in different colour ways:
View attachment 483644
Comparing the official cosmonauts chronograph to one of the classic chronographs, they do appear to be different sizes/shapes.
The classic has a thinner bezel, different lugs, crown guards...
Click to expand...