This means that over a span of 20 years, even with perfect use, there is a 33% chance for a pregnancy

No this is completely inaccurate and wrong…there's a 33% risk of a condom failing. You'd still have to time it with ovulation of the person you're boinking for there to be a risk of pregnancy. And even then, having sex in the most optimal period isn't even a guarantee of pregnancy, far from it.