What strikes me as bizarre....if someone planted those, why plant 3 (?) trees, different varieties, in the same spot? A landscaper would surely never do that? A beginning gardener wouldn't do that, either. They're practically in the same hole. None would have room to thrive.
In other words, those trees were not a landscaping decision. Something else is going on there.
Speculating here.... maybe more than one tree/variety had to be planted because a) the hole was too big; b) just in case one failed; c) BM bought them and was too lazy to dig more than one hole; d) BM got anxious and over-thinky and decided "more is more", so "more trees = more effective for my purposes"; e) .....
Who builds a tumulus (burial rock or earth pile) these days anyway? This is not the stone, bronze, or iron age. It's the age of bobcats, no tumulus necessary.