If they are utilizing phosphorous credits, this would make sense. It would delay the start of construction but save some time on the back end along with a considerable amount of money.
In a nutshell, the county would place a large tract of land in a conservation easement, meaning it could never be developed. In exchange, DEQ would significantly lighten the environmental requirements for the smaller tract of land at THS. Grayson County did this when they installed turf a couple of years ago.