I guess I was under the wrong impression that most timeshares had the summer months in their Gold season
Many timeshares have the summer weeks in their Platinum season, because school vacation weeks are generally in higher demand.
Although the climate is pretty stable year round in Aruba, there is higher demand from Northeasterners trying to escape the winter cold, so the Platinum season season there encompasses those higher demand winter weeks. In Aruba the rest of the year is Gold. Other Caribbean properties have Gold and Silver seasons, with the Fall months during hurricane season designated Silver.
There are other beach properties and coastal properties where the weather is best during the summer (ex- HH resorts, NCV, Fairway, etc.) so those months are Platinum. And there are other destinations considered to have equal demand all year round (although certainly there are higher demand weeks than others), so they are Platinum only.