Looks very similar to what I had.
I ate several segments and flavorwise I thought they were great, just way to acid. But they had sweetness, lytchee like flavors, and apple / crab apple like flavors.
Mine had FALLEN from the tree and yours seem to be cut off. So maybe yours aren't at peak flavor as a result. Also, even if what we had is the same species (and it seems that way based on the photo) there could be genetic differences / growing differences that cause the flavor to be different.
And there was that weird gummy substance on the surface of the seed that stuck to just about anything.
They are smaller than mangosteen, that's for sure.