Right, I don't think that's the part that's counterintuitive. It's the claim he makes "if someone offers you a bet 70% chance to win a dollar, 30% loss, it's better not to take it in some cases" is what is counterintuitive to people.
That said, growth is pretty close to optimal even for smaller wagers. This plot shows growth rate as a function of wager size: https://www.wolframalpha.com/input/?i=plot+log%2850+-+x%29*0...