Does it drive strait ?
If so it was most likely deliberate.
There is no need for them to be identical.
Mowers suffer a torque reaction when the blades are running so perhaps it helps the mower to drive stait.
The owner of Spartan is a mower designer .
I have a 1966 BSA Victor enduro motorcycle.
The foot pegs are in different positions and the wheels are not in line with each other.
Apparently this is deliberate to make it fly strait & level and to counter the fact that the engine is off set to the right.
But to the uneducated ( me ) it seemed very wrong, but it does ride right .