That's the "but their case would still fail if the second author could show that their work was independent, no matter how improbable" part of the post you're responding to.

One out of ten to the power of "forget about it" is not improbable, it's impossible.

I know it's a popular misconception that "impossible" = a strict, statistical, mathematical 0, but if you try to use that in real life it turns out to be pretty useless. It also tends to bother people that there isn't a bright shining line between "possible" and "impossible" like there is between "0 and strictly not 0", but all you can really do is deal with it. Where ever the line is, this is literally millions of orders of magnitude on the wrong side of it. Not a factor of millions, a factor of ten to the millions. It's not possible to "accidentally" duplicate a work of that size.

It sounds to me like you're responding to a different argument than they're actually making and reading intent into it that isn't written into it.