My point is that the initial assumptions never hold because we can never say "We know this is how it is going to turn out". We can say "This is how we hope it is going to turn out."

YAGNI embraces this lack of knowledge explicitly, as you quote from the article, and my quote from five posts up.

We're not saying that YAGNI is always better in any specific sample, we're saying YAGNI is an optimal strategy across the entire range of samples.