Ask-a-Dave's-Gardener: ROOTBOUND Karley Rose Fountain Grass, 2 by EBGB

EBGB wrote:
I am fairly new to gardening. When I took a newly purchased Fountain Grass Karley Rose out of the pot it looked like what I think they call “root bound”. I separated the roots as best I could, planted it in good soil, and watered it well.

My friend told me I should have left it alone and planted it like it was when it came out of the pot because “Too much scarification can kill a plant.”

See the attached pictures. 001 is how it looked when it came out of the pot, 002 is how it looked when I sprayed the surface with water, and 003 is how it looked after I tried to untangle the roots.

What advice do you have on how I might have handled it differently.

Thanks in advance for your opinions.