Flywheel-type question

[Lightning II]

I’ve honestly never thought about this before:

Why are some flywheels specified with a Driver-Side or Passenger-Side starter?

I thought as long as the teeth match up to the ring gear then it shouldn’t really matter.

Here’s a screenshot of what brought my question on:

 

[Aspen500]

Imagine it has to do with the ring gear offset. No idea which is which but the gears are .850" from one another.