It does! I'm not sure what that person is referring to. git log can even use ASCII art to depict the relationship. Most modern git web frontends depict the relationship. Sourcetree, gitkraken depict the parent relationships. I wonder if we're misinterpreting? But the parents are distinct from one another, the hierarchy is not lost on merge. Part of the reason I prefer merge commits rather than rebasing.
Note: they don't have to be exclusive. You can rebase a branch so the history is linear, then merge --no-ff and create a merge commit for it. This gets you something like the best and worst of both worlds.
