Peter,
I don't think there's a contradiction there, and I also think that you are right about using land that isn't any good for housing.
Let's assume for a moment that the Lanier GC has been a profitable golf business, and nets $500,000 per year, split between two owners. This is a viable business, but for an owner(s) to turn down $20 million for the land from a developer would be very, very tough. That doesn't mean the golf wasn't viable, except in relative terms.
Meanwhile, just a few miles from Lanier GC, the Love organization has built a course named Windermere, which is now part of a 15 club group of courses and a successful business also. However, unlike Lanier, which is basically flat with lots of road frontage, Windermere is built inside a housing development on land that probably wouldn't perk anyway. It was indeed left-over land. In fact, I think Paul Cowley once wrote on GCA that when they first saw the site, they didn't think a course would work there. It does, very well, but it took some really clever design to do it, and it sure ain't walkable!
All of this is a product of Atlanta expanding QUICKLY to the north. When Lanier was built, that land was cheap; it isn't anymore, and that changes the whole dynamic. Golf worked as a business, and worked well, but money talks.