Fruitlover, when dealing with the public, everything is confusing, no matter what you start out saying!
The genus name, Mangifera, means "mango-bearing". By definition, the fruit of a mango-bearing tree, is a mango.
So something like, "This is a casturi, a rare species of mango, which is separate from the well-known India-type and Southeast-Asian-type mangos, that most people know," is about as clear as we can be.