Brett...........
...........Not trying to answer for Tom D., but there IS an example of leaving 'potential grass roughs' alone during construction, RIGHT HERE AT OLD MACDONALD. The fire that burned from north to south during the early construction of Pac Dunes (winter of 1999/2000?) left open ground where gorse grew, right on the site of the now current Old Mac. That open ground was seeded to hard and chewings fescue, and has developed in the years since into mature, if somewhat spotty, rough.
When Old Mac was constructed, large portions of that rough sward were retained, and are in play on many holes today, most notably on 6, 9, 10, 11, 12.
That rough is one reason, IMO, that Old Mac feels so mature and timeless as a playing ground.
It is dense, tough, spotty stuff!!
Tom