Erin Hills, all 18 holes for stroke play, will be added soon.
WGT has an agreement with the USGA to add US Open venues WGT doesn't already have. We got all of Pebble Beach a couple of years early.
Courses have to want to be added. It's my understanding they also have to fork over some pretty substantial $$$$$$$s to get added too. If you can find a course that wants to added and can afford to pay the entry fee for them, more power to you.
Plus it takes WGT 6+ months to put together just 1 new course after they spend the 2 weeks or so it takes a team of photographers to make the 300,000 or so photographs they need to produce their 'photo realistic' online golf course.
https://youtu.be/M8h8XYbvum4