I think most of the mango trees in Fiji are seedling trees, and that is why they get large. Grafted trees tend to be a lot smaller. Then there are the super dwarf types like Julie that never get very large. I have a 20 year old Julie that i never pruned and it is only about 10 feet tall. Other mangos planted at same time, also grafted cultivars, are about 30 feet tall.
We have lots of volunter seedling mango trees along the roads here. I guess from people chucking the seeds out of their cars. Many are over 75 feet tall. They usually have quite small and sometimes very fibrous seeds, but very tasty.
Oscar