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