"

No, you're confusing ""small probability of drift"" with ""small drift"".  They're not the same thing.  Yes, it's less clear cut than it used to be whether drift can occur in large populations.  But when you're talking about random sampling, if there is any heterozygosity, then the probability of a change in allele frequency will never be absolutely zero.  But there are unlikely extremes allowed by any theory.  What we need to do is a better job of shading the issue.  It is absolutely true that genetic drift has traditionally been thought to be a non-issue in large populations, and that selection pressures tell the story over time. This is overly simplified though.   "