Nobody was challenging the notion that this was a single mutation.
As has been said, we have known that was likely the case for several weeks already.
But you said:
Latest advice is that the melbourne outbreak is caused by a mutation that makes its C19 strain the most infectious so far on the planet.
This, we challenged. And you still have shown no evidence of it.
And, no, being the "only" outbreak does not make it the "most infectious" strain on the planet. Putting "QED" in a sentence does not make it so. Perhaps it is, but so far evidence is that even the
D614G mutation has not proven to be any more infectious despite becoming prevalent in many parts of the world.