My grandfather died young, and the funeral home wouldn't sell my grandmother the plot next to him, because they assumed she would remarry. She never did, and when she was dying several decades later it really upset her that she couldn't be buried with him. But, my mom spoke to the graveyard, and since she was being cremated, they were willing to let her be buried in the same gravesite. My mom told her mom, and my grandmother's reaction apparently was "Oh good, I always wanted to try being on top, but he would never let me".
But, because of that, I definitely was surprised with the whole "we won't be together forever" thing, because urns can definitely be buried. Or you can scatter half and bury half, or whatever.