I don't get the sense that those varietals will only grow in Guimaras, but the locals will tell you that it's not just the varietal but also the specific soil,

I don't get the sense that those varietals will only grow in Guimaras, but the locals will tell you that it's not just the varietal but also the specific soil, micro-climate, and cultivation methods of the island that makes them special. I have no idea to what extent that's true, but while I've had lots of good mangoes all over the Philippines, the ones from Guimaras were definitely the best.