I love that old adage. Just want to pile on to the discussion here, adding absolutely nothing to it in the process. I love when we sink to petty arguments on semantics. Are we really splitting hairs here over .000000001% odds? I mean, I know life is boring right now for many of us, but jeez.
There's common use of language versus the language of science. Since the discussion drifted in to statistics and probability, the choice of words is expected to be precise. Calling a non-zero probability "impossible" may be functionally accurate because it is never going to happen, but, in the world of numbers and science, people typically choose to caveat the term.
There are reasons why. To use your example of .000000001%--is that the line where we say something is impossible? Why not .00000001%...or .001%? Where is one allowed to accurately use the term?
The odds of winning powerball are about 1 in 300 million or .00000033%.
But it happens.
Nobody would object to "it's never going to happen" or "for all practical purposes, it is impossible"...
ahhh...but the original scenario didn't include a bunch of caveats. It was simply 800 rated players having a better round than 1000 rated players. So...there is a tournament on day 2 where the lower rated players play in the morning and the higher rated players play in the evening. At noon, a front rolls in. Wind gusts 40 MPH and temperature drops from 60 degrees to 40 degrees. Those scores in the afternoon are going to suck. If one only looks at the numbers, then there is no explanation other than the 1000 rated players had a really bad day.
So, when stating, "it's impossible"...the next thing you will read is a bunch of caveats basically stating that all other variables are equal. Once that caveat is inserted in to the discussion over word choice, then the issue is settled. If caveats are necessary to make the statement accurate then it's just a matter of choice as to how one caveats the statement.