In an old 1939 home I have not had an inspector make me change that dimension.
Some old homes in Seattle are 7 feet for the bath. That meant 24" for the toilet and 24" for the lav.
Way too small by today's standards.
Unless you are changing the closet arm, I wouldn't worry about that small difference.
The Unifit does not change anything sidewise. Just front to back in 2" jumps.
Caroma does make a swivel adapter on their 270 bowl that allows for some shifting, it's a 10" to 12" bowl that allows for some sidewise shift.
The Caroma 270 bowl uses an offset adapter so you can adjust the rough-in from 12" to 10"
Or you can shift the bowl sidewise.