2003 exmark lazer z hp question?

Ok was researching exmark lazer z hp in the years from 2000 to 2003. What I found was that exmark put two different engines on these models. One was the Kohler Command and the other was a Kawasaki FH series. The frames and all components where identical, the wiring was different. Now looking at the engines shaft sizes: The Kohler had a 1" by 3x9/16 and the Kawasaki had a 1" by 3x5/32. The difference in shaft lengths are 10mm.

Now for my questions?
If all components are identical, why the...

2003 exmark lazer z hp question?