No. A loss of a child is a loss of a child. I have heard people say that parents of 4 or 5 children should feel less of a loss if one of their children dies, than a parent who only has one or two children. It just doesn't work that way.
Distance? I only have young, pre-teen kids, but based on my own relationships with my parents, the closeness we once had has shifted to my "new" immediate family. I expect there will come a time with my own kids where we're just not as "close" as we once were. I wonder if that has any impact on how some people process grief (it seemed to, from witnessing aunts/uncles who died before my grandparents, and how they processed it).
I can also add that a lot of my anxiety around the sudden loss of the child is the thought of their life being cut short. Everything that they could have experienced, all the potential -- gone. Sure, when you're in your 60's you still have lots of life left to live, but the weight of life being "cut too short" just doesn't seem like it'd feel as heavy as say, the death of a child, teen, or a young adult in their early 20's.
My Mum visited her Dad maybe once a week at most, but even in his 80s, whenever she visited he'd make her favourite sandwiches, try to give her money, take care of her car. She died in hospital, and he was holding her hand telling her she would be ok. It totally broke him - he had a series of strokes causing his dementia to worsen quickly, and he died within a year.
Obviously not true of every parent-child relationship, but when it is true, it hurts.