That has been tweaked slightly I think. Certain golfers, the more popular ones, are required to play in a tournament that they have not taken part in during the last 4 years. The idea being to make sure the smaller, less attractive comps are not completely ignored by the big boys. I can't discover what rankings this relates to but it does seem to be a thing.PGA members are not required to play any particular tournaments, as long as they fulfil the 15 event minimum (unless lifetime exempt)