I don't think it's a case of dumping. It's a great resort in a great location. I have stayed there on an exchange and would do so again. If you join TUG, you can access and read the comprehensive resort reviews (link to the database is at the top of this page).
However, the bigger the resort is, the more units that will be offered on the resale market. That's because owners change vacation preferences, have family changes, financial changes and other life changes that make them decide that a particular timeshare resort (or timesharing in general) no longer fits best for them.
By comparison: There are only seven resales at this resort listed on Redweek. Marriott's Grande Ocean, generally rated as the #1 timeshare on Hilton Head (of about 25 timeshare resorts there), has 22 resales listed. Is there dumping going on? No. GO is a big resort!