While it's really nice calculation, it's missing quite a lot.
It shows effect of less mass a wheel has, but pure inertia is only one portion of energy needed to spend to accelerate car.
Add rolling resistance of tyre, and ofc - resistance of going thru air, etc, etc...
So in the end, difference is miniscule.
While it's interesting in scientific approach, in simulator case (such as LFS), it can easily be ignored.