As someone who has composed aleatoric music and had many discussions with people who have devoted their lives to generative music, I have to say it's debatable whether what you described can strictly be called a "melody" unless you take the broadest dictionary definition ('a pleasing sequence of notes'), though I do think you can call it "melodic" as in 'melody-ish'. In other words, I think there's an essential difference between melody as conceived prior to the advent of generative music, which implies a decision by the composer that 'this is the melody', and a 'random melody' where that decision is made in a different manner, i.e. "whatever this process produces is 'the melody'". In the case of a randomly generated score, it gets a bit confusing because it's not clear if the composer used a generative process to determine 'the melody' or if it can meaningfully be called 'random'. Ultimately we just don't have words for such things. Perhaps conveniently, generative music still plays a very minor role in music culture outside of i.e. some of Brian Eno's recent work and the enduring influence of John Cage.

Aren't you then saying that melody-ness is being conferred by the composer? That would make it extremely difficult to confirm that something is a melody or not by observation alone (and thus likely impossible when determining whether other apes can come up with melodies).

That said, I think the article is not using "random" in the literal sense but in the sense of "arbitrary", as in "novel" (rather than being simply a reiteration of a previously observed tune).

In other words, random within a non-random subspace of the universe of possibilities. Like hitting random notes on a piano, without having a piano to start with.