Years ago they were with a different MSC and were discontinued. I see them listed currently as a client of a particular MSP, but it varies from market to market. The Chang's in my market is not shopped (nor on their list of clients) while the one in a friend's market is listed as a client but has not shown up on their boards.
It may well be that the Chang's shops are being picked off by the MSC staff before they hit the boards. One upscale shop here (not Chang's) was picked off for months before hitting the boards here. It is expensive and awful so now they can't get rid of them, though yes, because of the name I rushed in to grab it as soon as I saw it because it was excellent in another market.