Stepper motor step resolution up to 50000?

The full step resolution is 200. I learned that by software configuration, the step resolution can be hugely increased to 50000.

(Page 9 in "Getting Started with NI 7330/7340/7350 Motion Controllers and P7000 Series Stepper Drives")

Getting Started with NI 7330/7340/7350 Motion Controllers and P7000 Series Stepper Drives

I'm wondering how do they do this?

I learned that people can do "microstepping" to increase step resolution, but the accuracy of each microstep tends to be compromised. (http://homepage.cs.uiowa.edu/~jones/step/micro.html)

If this is the case then I would like to avoid such a "software configed microstep".

Or please if anyone can tell me how do NI achieves this.

Thanks in advanced.