[Someone]

You have to read that “more intriguing still” paragraph as being in the same scope as the preceding one, which says

> we can compute just 64 extra bits, and have a probability of 1 - 2⁻⁶⁴ of terminating. This is so close to certainty that we can simply stop unconditionally without introducing any measurable bias (detecting any difference would require about 2¹²⁸ samples, which is prohibitive)

So, it’s about a variation on the unbiased algorithm that is slightly biased, but gains some other desirable properties.