It's fair to take either opinion – personally I often find the common ancestor quite important, but I could understand why you might not. But it's disingenuous

It's fair to take either opinion – personally I often find the common ancestor quite important, but I could understand why you might not. But it's disingenuous to call a tool "three way merge" if it's not shown. If you're only showing the two immediate parents, that's a regular old two-way merge.