I thought lychee family but the description that went with the tree was as follows:
“Tree is large and similar shape to a mango tree, it's an evergreen. Found on the coastal area of central Q.
Has shiny long leaves with single predominate vein down the centre
Has these small green spiky almost leathery fruits that when opened have a dry fleshy first layer similar to a custard apple with a centre with small chilli sized seeds.
The leaves and fruit have no distinguishable smell.”
I agree lychee though, I think what he is seeing aren’t seeds.