Hm, interesting. I haven't tried halosulfuron-methyl with my kyllinga problem, I went with Dismiss(sulfentrazone). I do know that there is some soil residual that the sulfentrazone can provide to help suppress any newer growth, and I had good results with it. I can tell you that I didn't have near the amount of luck with the Prosedge that I tried on a similarly infested area of my yard that had goose grass and kyllinga in. I sprayed both areas with different products, and the sulfentrazone absolutely scorched my target pests, and I had mediocre results with the Prosedge.
My $0.02.
My $0.02.