Yes, the same amount of ice will cause the same amount of dilution. What they were using as a comparison metric is how enjoyable the drink is during the typical

Yes, the same amount of ice will cause the same amount of dilution. What they were using as a comparison metric is how enjoyable the drink is during the typical time it takes to consume the beverage (I infer). Most of the time the beverage is consumed before the ice has fully melted in my experience. The level of dilution during the time period in which there is still solid ice is what was being compared.