Very cool that this has been observed but I actually think this kind of thing is inevitable given the way viruses work and their rapid rate of mutation. We've known for many years that viruses like influenza use different parts of a cell to reproduce different parts of the virion. They can also mix up their genomes when multiple virions infect the same cell. Furthermore we know that this can lead to genomes to support each other, for example a genome that is great at infecting cells but poor at reproducing will end being reproduced by the machinery of a different genome. It's not hard to imagine this going the next step and not even requiring every part of the genome to be present in a cell.

Viruses are the most fascinating part of biology. An inevitability caused by a security flaw in the way genetics works.