I repeat: If you want to know why VSTEP made the choice that they did, ask them.
As I said in an earlier post, if the graphics were reduced in quality it was more likely to reduce memory use than to increase frame rate.
You are making a rather wild assumption that the graphics in the present game are substantially inferior to an early development effort, based only on some screen shots or renders—not on any actual knowledge of how the running graphics appeared.
You imply that VSTEP low-balled the minimum requirements. Why then do so many users with ostensibly more capable systems have low performance?